OK it should be fixed now - there was a rate limit which doesn't normally land but due to multiple Tor users coming through the same exit node, it was triggering the limit.

Nothing to do with the certs just told me a cert error because it never finished the handshake.

I tested through Tor on multiple machines now and multiple circuits and is working clean - thanks for the heads up.

I cannot see what is causing the issue, the certificate's full chain is sent, the clock is synced, the cert is showing zero errors in OpenSSL - so this is very confusing.

The irony is, you don't actually need Tor on my site because there is no logging, no third parties, no adtech etc. it is just static HTML files - so whereas I would normally recommend Tor I designed the site specifically to be privacy first.

I will try to figure out what is going on though because obviously I am fully supportive of people protecting their privacy with Tor.

Not sure why, it is working fine everywhere else - I see in Tor it gives an invalid certificate error, but the Lets Encrypt certificate is working fine in other browsers, so seems to be a Tor thing specifically.

I will investigate.