Questions on when to update a existing iApp

Have the below questions on F5 iApps

1. We were updating a cert on one of the exchange iApps and it worked well on one device but through a error "01b4002b:3:Client SSL Profile (/Common/test-exchang.app/test-exchang_clientssl): the profile has no RSA/Key Pair that can be modified" on another F5.  Was able to apply the cert on the iApp using a workaround, Applied clientssl cert and later updated to newcert, it worked.  Is there anything we need to check? What is the permanent fix for this, Do we need to update the iApp?
2. How do we update a existing iApp. I see the same iApp version when I download