Typically the issue may arise due to:
To check whether your website receives enough traffic for HitTail to be able to operate, please do the following:
If there are less than 1000 clicks, you may have not enough traffic to get any hot keyword suggestions. In this case, we suggest using the Keyword Ideas tool instead. It generates long tail keywords based on your entered phrase and can be used to get valuable keyword ideas even if you’ve just launched a new website or a blog and don’t have any traffic at all.
If you have more than 1000 clicks, it is very likely that you just haven't linked HitTail to your Google Search Console properly. Here is what you need to do:
Note! If you see two entries for your domain in Google Search Console (one with “https” and the other with “http”), please add the email@example.com user to both of them.
If you still can’t setup HitTail, please feel free to contact HitTail support.