Hi patu, the problem may be that the extension was checked into the database but no on the ePO server.
Try to open your database with SQL Management Studio (or SQL Management Studio Express if you're using SQL Express) and browse to Databases->EPO4_XXXX->Tables and look for OrionExtensions (or dbo.OrionExtensions). Then right-click over it and select Open Table. Here you'll find all your extensions (as well as the EEADMIN extension if installed).
Look at its version and then comparte it with version shown under \\172.16.48.81\c$\Program Files\McAfee\ePolicy Orchestrator\Server\extensions\installed\your_extension_folder (inside this folder you'll find another one with your extension version)