To resolve the issue, do the following steps:

1. Download the server.ini from the Apex Central / Control Manager (TMCM) server using the URL below:
   https://<Apex Central FQDN>/TVCSDownload/activeupdate/SERVER.INI
2. Open the SERVER.INI file using a text editor, and verify 3.5.2141 version or higher exists.
3. On the OSCE Server, backup and delete the contents of the AU_Cache folder in the following location:
   ..\PCCSRV\Web\Service\AU_data\AU_Cache
4. Perform another manual update on the OfficeScan Server.
5. After update is complete, see if the 3.5.2141 version or higher now shows in the Plug-ins tab for upgrade.