Some UJAM plug-ins are only available as VST2 and not VST3. Please make sure that Cubase actually displays VST2 plugins!
Cubase sometimes treats Plug-ins as 32bit software although it is 64bit.
Solution: Uninstall Plugin (optional: delete all Plug-in files), do a rescan with Cubase, then reinstall the Plug-in.
Sometimes Cubase treats the plug-ins as 32 bit software, although it is actually of 64-bit architecture and shouldn't be recognised as 32-bit. This seems to be a general Issue with Cubase (10.5), which somehow tends to randomly mark plugins (from all manufacturers) as such.
To get rid of this issue, start with a simple task and remove the plug-in files. Here's an example for Virtual Guitarist CARBON:
Please delete Carbon and all its files from the following folder:
This article explains how to delete all plug-in files (in most cases that's not necessary):
After uninstalling the plugin, please run Cubase and its Plugin-Manager, do a rescan, and close Cubase.
Then, re-install your plug-in: