Getting OTA version is not compatible error after patch upgrade

We are currently using QC 11 patch 15 hosted in a JBOSS server. We tried to upgrade it to patch 19. After the patch upgrade, we are getting the below error on login.
"OTA Version is not compatible with the Application Life cycle Management server."

We were able to logon without error prior to the Patch 19 installation. The issue is reported only by the users who were able login to the application before patch upgrade. But new users are able to login to the application.

The URL used by the users are proxified. The cache in the proxification servers are cleaned every day. If we try using the application without proxy setting, its working fine. But we cannot remove the proxification as it is done on the enterprise level.

Kindly help me in rectifying the issue.