googlebot: the Google desktop tracker that shows unreachable: the mobile tracker works

I noticed a sharp drop in Adsense earnings on one of my sites this week and, after doing some research on the Search Console, errors were found that suggest there was a problem with my robots.txt. I checked this and it's absolutely fine.

When I went to the old console and ran some search like Google (desktop), I got inaccessible for all the URLs I tried in that domain (included /). However, when I tried the mobile tracker, everything was fine, including the rendering.

A little background. I host several websites in a shared IP address. I recently moved the server / IP address. This was about 4 weeks ago and I have not had any problems until a few days ago, and only on this site.

I run application firewalls (Fail2Ban and mod_security), but again these should not have changed suddenly. Also now I have disabled them.

I have checked the site from a few IP addresses to verify that it works correctly and it is.

Any idea – or is it just waiting and seeing …