Fill & Sign - Add Signature freezes Acrobat

I've just bought and installed Acrobat but when I try to Add my signature using the Fill & Sign > Sign Yourself > Add Signature option, Acrobat screen just goes black (see attached) and I can't click on anything.

Initially I thought I had to end the task using Task Manager. After many more attempts with other documents, after checking for updates, after a restart, after running a repair, I discovered that Esc works to get me back to the document. But I still can't use this option to add my signature

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