Problem accessing addons in third party repositories in windows



I’m new to Kodi, and am having a problem with add-ons on windows 10.

I’ve got Kodi installed.
I’ve added a source using File Manager -> Add Source.
I’ve added a repository using AddOns -> Install from zip file (and then choosing the zip file in the added source).
Kodi tells me the repository is installed.
But when I then go to AddOns -> Install from repository and choose that repository, Kodi just hangs (with a blue circular busy indicator).

If I choose Install from repository and then select the built-in official Kodi Add-on repository, I get the list of AddOns just fine.

I’ve tried the above with 2 different third part add-ons (RisingTides and TheLab) and got the same result.
And I’ve tried this on 2 different windows 10 machines and got the same result.

On my android device, installing add-ons from the same 2 repositories has been seamless.

It feels like I must be missing something fundamental so I was expecting to find other people describing this problem… but I’ve searched and found nothing.

Can anyone tell me what might be going on here..?