Need help with renewing SSL certificate on custom port

[Guldstrand]

Can someone please, please help me to fix my issue with enabling SSL.
I installed Azuracast (radiopanel) for almost 1 year ago, and all worked great.

I'm not sure whats happend the last month, cause i have issues with creating new SSL-certs.
Azuracast is installed on an own server, (behind port 8443).

I have a separate server from before which already uses ports 80 and 443 for websites etc. Therefore I am forced to use a custom port for Azuracast.

Again, everything worked fine from the start, don't ask me how.
But now the radio stream does not work, due to no SSL certificate.

I get the following error when I try to create a new certificate in the Azuracast panel:
Challenge validation failed: IP HERE: Invalid response from https://MY-DOMAIN/.well-known/acme-challenge/xYQP7DEJ-85ao70juwq7jtAXjXUE4e0dMZRhFltBuSE: 404 (urn:ietf:params:acme:error:unauthorized) at /var/azuracast/www/vendor/skoerfgen/acmecert/src/ACMEv2.php:145)"}

[kicken]

Is whatever server is running on port 80 using the same domain?  Let's encrypt doesn't all alternate port numbers so you either need to be able to validate the domain using the server on port 80, or use an alternative verification method such as DNS verification.  Once the certificate is validated on port 80, you can use it with other ports just fine.