Hi @xxbb0709, Thank you for the detailed report! It seems this may be related to how the VPN connects to Google/Firebase services from China, although we cannot yet completely rule out other causes. Here are a few things you could try:
Clear your browser’s cache and cookies for Language Reactor, then try logging in again.
Try logging in using an incognito/private browsing window.
Try a VPN server in a different country (not just a different server in the same country) - some locations connect more reliably to Google services.
Check if your VPN is known to work well with Google services specifically, as some VPNs have unstable connections to them even when the rest of the internet works fine.
Please let us know how it goes.