Check the Analytics code
The first step is to confirm that the Analytics code is installed correctly. This is because it is common to look at Analytics' null traffic and believe there has been some sort of penalty.
However the problems can be, just the lack of the Analytics code or even the installation of the wrong code. Now if Google Analytics is set up correctly and when we click on an organic result, the tool points out that access has been computed, it's time to move on to the next step in our framework.
Go to Google Search Console
Just go to Google's own tool and check the Search Analytics tab for how many clicks you get from Google. Just look at the chart to find out if it's normal, make sure your site is up and there is no problem with it.
But remember, it has a small delay (of two days). So the important thing is to always check the dates, so you'll know that if the information you see in Analytics is reflected in Search Console, especially if traffic has dropped yesterday or today. Therefore, if even in the right time, Search Analytics still seems normal, there may be a problem with the configuration of Analytics itself, especially in the redistribution of organic.
If your organic accesses are gone, stay tuned to the robots file. Remember what the robots.txt file is? It is a file in which you can place directives so that the search tools do not read some items. But how important is it? It is common that many companies that arrive with new sites have the page totally blocked in robots, thus precluding the reading of Google. After all, this directive will bring down your organic traffic.
Error in Canonical Tag
What happens is that at the time of implementing the canonical tag, if you are not very careful, you may end up telling Google that a series of pages are actually only one. This causes you to lose them in the index and also that loses the potential of organic reach of your site.
Most worrying causes
It is worth remembering that usually the problems that happen with your page are sent by messages by Google within Search Console, except when the problem is an algorithmic penalty. That is, in some cases of manual punishment, there is a notification in Search Console notifying you that you are violating Google's guidelines.
Already in algorithmic penalization, the only way to know is to follow market trends. This often requires a more experienced person to identify and work on recovery.