Plugins don't seem to be upgraded in WP Workbench Manager

This is exciting. Thank you for all the time, attention and care you have put into it.

I tried updating a few plugins, it shows success, and then cleaning the cahc, but the actual update doesn’t happen. I tried it with a few different websites and different plugins, all the same.

Where would you suggest me to look to find out more about it?

Thank you again.

I’m pretty sure that’s not the case. In fact, this is simply impossible, and I just double-checked it—it works just as expected.

You’re most likely mixing up instances.