My forum has been having a server problem for a few days now.
The hosting company says there are no problems with the server.
I have other sites on the same server and have no problems.
How can I solve the problem?

https://www.forumnauka.bg/

The following error occurred:

The Service is not available at the moment due to a temporary overloading or maintenance of the server. Please try again later.

Please contact the webmaster with any queries.

11 minutes ago, crackingbg said:

My forum has been having a server problem for a few days now.

Were they any changes/modifications made to the forum prior to this happening?

Can you check your Server Error logs and see what messages have been logged in there since the time that the error happened at your forum?

35 minutes ago, crackingbg said:

The following error occurred:

The Service is not available at the moment due to a temporary overloading or maintenance of the server. Please try again later.

Please contact the webmaster with any queries.

This kind of error is not something Invision Community shows. Your server is showing it after something triggers it. Only your hosting can tell you what the trigger is, though.

Yes, the problem was with the server.

Glad to hear you were able to resolve the issue.