Unable to create an account and sign in to self-hosted server using Web app not self hosted (Failed to fetch)

[sebgeekinside]

When I try to create an account and sign in to my self-hosted server using Web app (https://app.standardnotes.com/), I've got the message: Failed to fetch.

Same message using the Android app.

I use Traefik v2 as reverse-proxy and as certificates resolver in order to secure HTTP traffic of my server.
The URL https://my.domain.com/healthcheck returns OK.
SSL checker of the URL https://my.domain.com/ returns OK.

Is somebody can help me to resolve the problem?
Maybe a Traefik configuration to make (middleware ?)...

[ChesterHCopperpot]

I've also started having this problem. My Desktop app has stopped working. I signed out of the workspace and tried logging in again, but it still says "Failed to fetch"

Interestingly, if I pull up my custom notes server in a browser, it says its there:

But if I ping the notes server in my terminal (ping notes.example.com) it repeatedly times out.

How can my SN instance respond with HTTPS to a browser on port 443 but not to my terminal ping? Pinging other instances on my VPS (eg: ping matrix.example.com) work fine, so my server is up and HTTPS certs are working. Interestingly, my mobile app (Android) seems to say it is syncing fine (green check mark). So I wonder if it's a bug in the web/desktop apps.