Link building can be seen as a part of SEO. With more backlinks pointing to your site, search engines will find your website a lot easier, and rank it better according to your specialty and niche. However, there are times when all those efforts can create little to no improvement to your website's ranking.
The reason for this not from search engines' crawlers not getting your links correctly, but because of how the link is representing itself.
By the time you have your website up and running, you'll want to make your website visible to search engines and your potential visitors. You have already created some contents, and search engines have indexed them as intended. Your website is performing well, and what you want next is to rank higher in their algorithm.
For quite a long time SEO specialists have concluded that more backlinks translate to better rank. In most cases, that is true. The more backlinks you have, the better the visibility your site has, the better it will rank. However, in some other cases, your backlinks won't do any much good.
Bloggers, website owners and webmasters have long set their challenge to build more and more backlinks, and are expecting their process will aid their website's credibility and ranking. They look into various link sources such as social media networks, other blogs, guest posts, forum boards and anywhere that they can put their links to. They may succeed in doing so, but when they fail, they starting to doubt the power of backlinks.
To some extent, link building is not as effective as it used to be.
More links can translate to minimal gain, or even worsen the situation. You can use your favorite backlink checker to see your progress. But don't ever consider your work is done when you see high gains, or give up when you see no results.
To help you understand why your backlinks don't work, you need to think outside SEO perspective, and back to the human nature.
Good Content, Bad Links
What you see is not always the thing that you get. What's presented on the web that aims somewhere, is not always as good as it seems.
Your links have to aim for somewhere. It can be your website's homepage, or other landing pages you have, or some specific contents you own. If you do have unique and useful articles that benefit both search engines and your visitors, you succeeded in creating one compelling content. But if the links aren't good, your backlinks won't do much good either.
The answer to this situation goes into broader terms. But for a lot of time, this could mean a low domain diversity. You may have a lot of links, but if they come from the same place, search engines have the potential to see those links as not particularly worthy.
The reason for this is because the status of the website you're putting your links into. If its page has less to no authority, search engines may see it as unnecessary, and won't move you up on its rankings. Particularly for competitive search queries, if your links are coming from low-valued websites, your backlinks won't help you much in gaining their attentions.
Another possibility is that the website you're putting your links into, is not relevant. Or if the website also has other links (too many links) that points to external sites that are manipulative or scam. Under this condition, search engines may set the whole links as not trustworthy to some extent.
The next that comes to probability is the location of the links. If your backlink resides near other backlinks with various niches from other websites, or shown in just a single place on the page, search engines will see the website that hosts the links as doing promotional method. Despite this is not at all a bad idea, search engines don't actually like these links, and they may consider those links not worthy enough to rank your site.
Good Links, Bad Content
Search engines are evolving, and to do that they have to learn about people's search queries in order to give what's best for them. You may have backlinks coming from great websites, but if the links aren't pointed to the great piece of information you're promising on the link, search engines disliked it.
For example, a long-tail keywords compete for the best combination of words. If the demand of a specific keyword rises, it won't necessarily rise other keywords that are relevant to it. Search engines are trying to give the best answer to users' queries, by giving them a broader information for its top results.
The poor performance of links in this situation may come from your website as well. For example, you have a high bounce rate because your website is loading too long, or its layout is not properly designed, or its browser supports aren't great.
The Brand Behind Everything
Google and other notable search engines don't mind how your domain name looks like, at least not by much. But as you build your marketing efforts on the web, you're starting to build your own brand eventually. When search engines have seen your brand, and categorized it according to your industry/niche/type, they're hoping to see more interesting things from you that are limited within your specific category.
If your contents, and links, are not representing your brand's image, or your domain isn't associated with the topic you're creating, search engines are not getting what they're expecting.
Branding yourself on the web is what makes people recognize you when they see you. If you have built your brand, people are expecting something from you when they see you. But when you can't give what they want, search engines might perceive you as spammy and manipulative, although you're not.
This can be very frustrating, especially when you see search behavior are biased on the brand itself. But if you're building a brand, your contents should somewhere work around the keywords people are expecting to see. The reason for this is because search engines are trying to take the human role, and see things at the human's point-of-view when they're ranking your website.
Technical Problems
When it comes to accessibility, your website's pages availability is one of the most important factor. When search engines' crawlers manage to find your links, it will try to access your site to see if you content has any relevancy in it, and rank it accordingly. However, if your server returns an error, or your site won't show the content properly, search engines will not like it.
In some occasions, search engines will see if they have your page's cache saved on its servers.
Your website, and all of its pages, should be available whenever your visitors need them. Search engine visitors are just like human visitors. If they see what they like, and somehow find your content relevant from the link they have been given, they'll like it. If they find you website, or your page, irrelevant, or if your website and its pages are inaccessible to them, most people won't look back when they venture onwards, away from your site for many moments to come.
Related: Administrative Relationship, And Why Google Thinks It Needs To Know What Websites You Control