What method are you using? It's not possible to add a card on mi mix 2s, https://xiaomi.eu/community/threads/google-pay.44165/page-3 there's already a thread in mi mix 2s subforum:)
I just tested it and if I press on "emulate" it says it was successful and it turns from red or green(not sure which one it is, cant see these 2 colors :D) to blue again. Tomorrow I can check if it's working in university
That's a known problem. Next time just type your wifi password where you'd normally put your xiaomi account and copy it, than you can just paste it even if the keyboard wont show up:) Or connect a keyboard with USB OTG
Delete the files in /cust/cust folder and reboot. That was how you did it with miui9 on the mi mix 2s, should still be the same... However just move the files to your download folder or something in case you need them:D
Where did you buy it? If it's less than 3 weeks old you should be covered by warranty for sure. You should contact your seller before disassembling your phone
First of all, I would make sure if your charging pad is working, the cheap ones tend to break. If you are sure your hardware is working maybe a clean flash of your current rom may help
Is it possible to just dirty flash updates(it's not shown in the updater application for me, should it be there?) or should we do a clean flash all the time