This is normal as the certificate will not have any IP Address in the names of the Certificate (Common Name or Subject Alternate Name list)
You have to use the FQDN of the server not the IP Address.
You could also check the SRV record sipinternaltls and check to which server it directs you (that should be the FQDN of the OCS Server, and then I assume that you use the Domain Name as the SIP Domain Name)
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