There has been a change in the Let's Encrypt's root certificate, which will cause the SSL error. You can read about that here:https://letsencrypt.org/docs/dst-root-ca-x3-expiration-september-2021/
The change shouldn't affect all browsers, it should work on newer browsers/devices, but it seems it affects some others. Our Engineering team is closely reviewing the change for a possible fix to minimise the impact (if possible).
Your patience in this issue is highly appreciated!