How do I fix recovery server problem?

When you buy a used Mac the VERY first thing you do is follow all the steps in What to do before you sell, give away, or trade in your Mac and then you have a good starting point. If you do not follow these steps you will have a mess that will never get cleared up!

You can't fix a remote server, you can only access or not access it. If you can't access it, there's going to be a local problem or a problem with your ISP to deal with.

The server itself may be busy but no end user can touch it without some pretty sophisticated hacking.