Basecamp keeps asking where the map is.

I have been getting on very well with Basecamp planning our trip to USA. A lot of work and a lot of waypoints!

Then I thought I'd lost the lot. Not sure what happened but I restored the Basecamp files from a backup and only lost a day's work.

But now, each time Basecamp loads, it asks me to Browse to where the installed Europe map file is (copy installed by Express on PC at C:\ProgramData\Garmin\Maps\City Navigator Europe NTU 2018.30.gmap). It never lets me select anything though I get it to the directory as the button stays permanently at "OPEN". I press "Cancel" and Basecamp opens and knows where the map is!

The USA map is installed on a USB stick and it has no issues with that.

I now just press Cancel without Browsing to the directory, and Basecamp opens, but it's a niggle and I have no idea why it's doing this. Hope someone can help, please!