Using AECOsim update 4, missing workspace / workset not found alert, preventing file from being opened.
Has anyone seen this message before?
Are you updating AECOsim Update 4 with OpenBuildings Update 5 ? , if you are doing so then it is not recommended for this specific release because there is a brand transition happened from Update 4 to update 5. I'm suspecting this could be the reason for your issue.
It is recommend that you first uninstall AECOsim Building Designer and then install OpenBuildings Designer. If you proceed with the update, It will replace any earlier versions of the product, but the root directories ..\Program Files\Bentley\AECOSim CONNECT Edition and ..\ProgramData\Bentley\AECOsim CONNECT Edition will remain branded AECOsim instead of OpenBuildings.
Please see the wiki Installation options for OpenBuildings Designer, this will help you.