Problem

Operations Agent processes fail to start after upgrading from the Operations Agent version less than 12.12 to 12.24. It throws the System.txt error.
(sec.core-76) Could not decrypt data. Incorrect padding.

Cause

With Operations Agent 12.24 Blowfish and DES algorithms aren’t supported. Therefore, during the upgrade, the certificates are migrated. This error occurs only if migration of certificates fails in any exceptional case.

Solution

Remove the existing certificates and request for new certificates after setting the secure configurations. For more information, see Configuring the Security Component with Hash Algorithm

For More information's, Please ref;

https://docs.microfocus.com/doc/Operations_Agent/12.26/OAfailstostartPostUpgrade