Yeelight Strip Plus Will Only Connect via China Server

I had a perfectly-fine-working Yeelight Lightstrip Plus, which went “offline” (1) from my app one morning, and would not reinstall, giving a ‘connection time out’ after every new reset and attempt.

I followed instructions in previous posts about this type of problem, eg, this one:

I reset the device and setup via a different hotspot on a different server (I use Europe, but followed the advice and switched to China mainland for the new install).

I managed to get the device working, the firmware was up to date, so I then followed the advice to reset and try install on my normal setup (my main router, and Euro server). But this just left me back at step (1)

Where do i go from here?