Make sure that the certificates for any registered servers that ePO - On-prem communicates with are supported by ePO - On-prem.
ePO - On-prem might not be able to connect to registered servers that use less secure certificates, such as certificates with RSA public key lengths of only 1024 bits. For more information, including additional supported public key algorithms and key lengths, see KB87731.
Note
TLS 1.0 is disabled by default for communication to external servers, such as SQL Server. For more information about TLS support, see KB90222.
Use certificates with RSA public key lengths of 2048 bits or greater for the registered servers that ePO - On-prem connects to.