Hello. My .htaccess file content is not visible in the all in plugin area but it is there in the file area. What is the reason for this?

Could be permissions problem.

Where and how do I solve this? If you mean the permissions for dadabase or user, I have full permissions.

I think that's also the reason why my main domain doesn't appear in the Google search when I enter my domain, only the categories appear.

Could this be the reason why my main domain does not appear but categories and regions and cities: MANAGE CUSTOM META TAGS FOR REGIONS?

In FileZilla set 644 permissions for .htaccess file.

Thanks but that is also on 644

I have now inserted the content into custom and copied it from custom and inserted it into the original and made it visible again in the allinseo plugin, but now the same content is in custom and original, is that a problem?

I edit .htaccess file only in cpanel.

Install Google Search Console to see what pages are indexed.

11,753 urls are indexed, well, I'll wait and see what happens in 1-2 days due to today's changes. Thanks for your help

Original one is backup only for your reference.
You can also update manually on server if you think there could be issue with permissions.