Local Router Error (similar to existing, but more detailed)

New install on Windows (32gb.RAM 2 x 1tb SSD drives and 1 3tb magnetic HD; i7 6800k processor). Imported site from a duplicator backup. Site SEEMS to be running ok (but amazingly slow given my machine).

If I go themes and try and add a theme or activate a theme, I get the Local Router Error. Have already tried restarting and rebooting.

I am new to Local and testing it out. So far, not so good.

Any pointers?

For installing the theme I am doing an upload of the DIVI theme (from Elegant Themes) and then trying to activate it.I see a similar topic, but there was no help on that topic.