Kepware server OPC - UA communication certificate issue

We are using Kepware server as OPC UA server as well as OPC UA client in two different machines. When I try to connect Server at Client, Server's certificate is automatically getting fetched in Client's 'Trusted servers' tab of OPC UA Configuration manager, which I am trusting manually. Similarly, when I again try to connect Server at Client, Client's certificate is getting fetched in Server's 'Trusted Clients' tab of OPC UA Configuration manager , which I am trusting manually. However, again when I am trying to connect still I am getting 'Client or server certificate invalid . Configure or verify the certificates' log in Server and not able to connect.  With Security policy set as NONE the communication is working, hence there is no TCP port connectivity issue, but when Security Policy: Basic256Sha256, the communication failing. I tried reissuing certificates using OPC UA Configuration manager and manually exporting and importing certificates from Server and Client but same issue is coming. Please let us know how to troubleshoot this further, is there any logs which I can enable to know what exactly is causing issue?