ZwiftLauncher has stopped working

I’ve been using Zwift for over a year on iPad and sometimes Windows 7 (work laptop). Just recently I got a new Windows 10 laptop for work, so I decided to dedicate my old laptop to Zwift. I used it a few times, then one day Zwift failed to launch - it worked one day and not the next despite me not using the laptop for anything else in the meantime. I’ve tried reinstalling and reinstalling after cleaning all references to Zwift from the machine and reinstalling to a different location, but no change. I don’t see anything useful in any logs I am aware of. Now obviously something has changed, but I don’t know what and I’d appreciate some suggestions on things to look at to diagnose the problem.
Oh and Zwift does still work on my iPad and new laptop (on the same network) and RGT and Virtugo work on the old laptop.
Thanks for any help