Just in case anyone is experiencing the problem I’ve just dealt with:
After installing a Windows 10 update today I was asked to enter an activation code for Dorico.
After a lot of messing about trying various options, I eventually found that there is an update to E-license Control Center which was added this month.
After installing this update, without any further action, Dorico opened again.
I can’t be sure that nothing I did in terms of attempting to re-activate the license had any affect, but I would recommend that anyone in the same position should try installing the latest eLicense Control Center first.