Quick Add New Term not working and no error is shown

 I am using SDL Studio 2017 with Win 7.

Both Studio and MultiTerm are up to date. 

My project has a local TM and a local TB, I can see some terms in the Termbase Viewer that I added in 2017. 

But now when I try to add a new term to the Termbase, either using the classic Add New Term or Quick Add New, the term is not displayed nor added. I do not get any error, either.

What can I do to fix it?