Btw I only have an Hub M3 (which supports Matter), so it’s possible the setup in your case is a bit different (just like in this case with the W100).
So maybe you’re not able to change the firmware after all… I switch all my devices to Zigbee, but I have an M3 that supports Matter sooo it’s a different situation.
Maybe there’s a bug in the newer version of Aqara app that blocks the ability to switch firmware if you don’t have any Matter hub.
I recall people on this forum just used Aqara app to switch firmware to Zigbee and then added their devices to third party Zigbee ecosystems, so the method we showed you had definitely worked before for other devices.