If the number of certificates allowed is exceeded, Patch Manager displays an error message when you attempt to retrieve WSUS or computer information, run reports, or perform configuration management tasks. You might also see errors that indicate the "RPC Server is Too Busy," or installation errors due to too many certificates.
This error is caused by having too many certificates in the Patch Manager server's Trusted Root Certification Authorities certificate store. If there are more than 200 certificates in this store, Microsoft's algorithm for searching and scanning the store fails. Patch Manager warns you during installation and upgrades if you are over this limit. However, it returns the previous error message if you add new certificates and exceed the limit after you have installed Patch Manager.
Error messages related to "exceeding the number of certificates allowed" include:
The KB article, ERROR: All management servers are unavailable for management group. 200 certificates, provide detailed instructions on how to reduce the number of certificates on the Patch Manager server. Additional information is available from Microsoft in the article, SSL/TLS communication problems after you install KB 931125.