@janjal
hmm...power reboot should've worked. I can only guess a few more potential solutions - but totally guessing now.

1. Download a PING app. When you're having WeChat problems open the PING app and try to ping your primary or secondary DNS. If that works then try to ping a known IP or DNS, such as WeChat.com. The PING should theoretically time-out (fail) meaning you're DNS resolution is failing (converting a .com name into an IP address). The PING will indicate if it's a DNS issue. If you don't want yet another app on your phone - use your webbrowser to see if you can connect to a known commercial domestic site - such as gokm, tmall/taobao, etc.

2. If WeChat is running in background mode - including after a power reset (auto-start) - try cycling the app - deleting the app (NOT from the phone, but from the list of apps running in background mode).

3. Check for application and OS updates (low probability of success).

4. Clean up your app database - if you rarely or never delete conversations with pictures etc - this can cause instabilities in the app. eg my outlook app wasn't updating emails from the IMAP server correctly. I had crud dating back a few years - so I migrated all emails to the computer from 2019 and earlier - cleared the IMAP - voila - typically poorly designed and programmed Microsoft app started working consistently and normally again.

FYI - I frequently have wechat pay problems using outside wifi, so I ALWAYS use mobile WAN for WeChat pay.