Problem
ERROR 31: The certificate associated with this Connection Entry no longer exists or failed to open.Please select another certificate.
upon trying to connect through VPN.
Cause
The certificate doesn't exist or failed to open.
Possible resolution
If you have installed a new certificate and removed the old one, you need to enroll the new certificate.
Either delete the previous connection entry and create new or modify the certificate authentication entry for existing entry.
Go to connection entries -> Right click the respective connection entry -> Click Modify
Within certificate authentication section , select the new installed certificate.