Windows 10: screen sketch not capturing my desktop

I've just discovered Windows Ink, and sketchpad works fine with my graphic pen + tablet. However, when I tried screen sketch although I could draw on the desktop image, when I saved a png it only saved the ink not the background image. Any clues what I'm doing wrong ? Do I need to be signed in for Ink to work - I just use local account.

My pc is up to date - video drivers, CU etc. I haven't installed any graphic tablet driver - it just seemed to work. It might be a bit difficult find any tablet drivers - made by AGK and I got it in a bargain bin at the supermarket several years ago. I doubt it's a driver problem since I can draw OK.

Any suggestions welcome.

Hm, I didn't used Windows Ink, does this software have layers? Maybe you have to select all layers (with background) to save it. with BG.

I'd forgotten about this post.

It was my rubbish old graphic pen/tablet that was the problem. I bought an entry-level Wacom (CTL 671 - about 22 x 17 cm £85 at Amazon) and everything works fine now. I find Ink really useful - I do a bit of 3D design using Cinema 4D, and use Ink + Wacom on my 2nd monitor for sketching out ideas, doing math equations etc. I've tried other software, but full screen Ink on a 27" does just what I want. Sometimes I feel like Sheldon on Big Bang Theory with his white board.