Try different browser ?
without seeing the actual error message, your pc and the server could not complete the TLS handshake to get the “secure” connection.
Are you using a vpn by chance?
It may just be traffic congestion on the path to their server, their server is overloaded, or something similar. If it was working fine before, was there an update to your browser about that time or any package updates on linux ?
it could be they did an update and something is misconfigured on their end. Definitely let their IT folks know.
Regarding the “cannot find” message, that is a DNS server lookup issue. Could be a time-out. Who are you using for your default DNS server ip address .?
is it your ISP or someone like cloudflare, quad9, google, etc ?