OK, I did the following:
1. I created a new db in PT3
2. I converted my PT2 db to SQL
3. I opened PT3 and chose "Convert PT2 DB", I don't get any errors but the popup window listing all the db's is empty.
What did I do wrong?
EDIT: Hang on, while I was writing this my PT2 db appeared in the window... (Still weird - is first says "Loading...", then the list is empty and after some time the PT2 db shows up.)