What version of Cubase were you using when Legacy Cell last worked ok?
The only way I’ve been able to use LC since Cubase 8 is to use jBridge. If you want to use LC, and want to have go at this clunky way of doing it, here goes. Install jBridge, install the 32bit version of LC to a folder Cubase can’t see, mine is at C:\Program Files (x86)\Steinberg\VSTPlugins
Start jBridge, follow prompts to install the bridged files to a folder, I have them here: C:\Program Files (x86)\Steinberg\jBridged.
You then point Cubase to the ‘jBridged’ in the Plugin Manager and you should be good to go.