Google Search Console generates multiple 403 errors

[Ordovicium]

Solved it. I tried many things due the hoster said it is a client issue and could't find any solution. Therefore I thought it could be a vBulletin setting which have been done and have to change. But with many discussions with the hoster we finally found a wrong setting on the hoster side. Thank you.

[Wayne Luke]

You haven't provided any information that allows us to determine what the issue actually is. Starting with examples of the URLs that are being forbidden would be a start? Are these URLs that should be viewed by Guest Users?

[Ordovicium]

Any ideas? My site is disappearing from the search engines, and I have no possibility to prevent.

[Ordovicium]

Hi,
Since a week, I have thousands of 403 errors from my homepage www.informatik-forum.at. If I visit the site with the browser I don't facing any of this issues. My hoster says, there is no blocking of any search engine and see the error on my side. But it appears from one to another day.

I have only a htaccess file which redirect from http to https.
The robot.txt isn't reachable too, but when to try it directly to open in the browser you will see it.
Any idea??