Hello and welcome!
Can you navigate to Administration > Certificates
Then delete the old certificate
Once the certificate is gone, go back to the vCenter solution/adapter in vROps and test connection and save.
If this isn't possible in the UI (Sorry I forget if you can do this in 6.2) Then try this KB: VMware Knowledge Base
Ensure you have a good rollback point before carrying this out.
A side note is that 6.2 is no longer supported by VMware so you may wish to upgrade so they can help you with future issues https://www.vmware.com/content/dam/digitalmarketing/vmware/en/pdf/support/product-lifecycle-matrix.pdf
thanks a lot for your help. It really worked....:)