Let's Encrypt cert gen not working

I have read many similar threads but I cannot see anything wrong with my current setup.

my hostname responds to ping from the Rpi that runs the local Blynk server, and from my client. This is an external dyn dns service, so not an internal dns.

I am able to browse to my hostname on 8080, 80 and 9443. 80 and 8080 redirects to blynk.cc.

This is my log:

changed values with USERNAME, HOSTNAME and EMAIL.

17:38:45.214 INFO - Using data dir ‘/home/USERNAME/Blynk’
17:38:47.727 INFO - Region : local. Host : HOSTNAME.
17:38:49.233 INFO - Initializing gmail smtp mail transport. Username : example@gmail.com. SMTP host : smtp.gmail.com:587
17:38:49.486 INFO - Reports : 0
17:38:49.487 INFO - Didn’t find custom user certificates.
17:38:49.491 INFO - Didn’t find Let’s Encrypt certificates.
17:38:49.491 INFO - Automatic certificate generation is turned ON.
17:38:49.492 WARN - ATTENTION. Server certificate paths (cert : ‘/home/USERNAME’, key : ‘/home/USERNAME’) not valid. Using embedded server certs and one way ssl. This is not secure. Please replace it with your own certs.
17:38:51.578 INFO - HTTP API and WebSockets server listening at 8080 port.
17:38:51.582 INFO - HTTPS API, WebSockets and Admin page server listening at 9443 port.
17:38:51.583 INFO - Mqtt hardware server listening at 8440 port.
17:38:51.616 INFO - Starting up certificate retrieval process for host HOSTNAME and email EMAIL.

It just stays there. Nothing happens with certs.

Edit: server.properties contains only two lines; server.host and contact.email

Hello. Try to enable debug mode in server.properties. It should print more info.
Most probably your host is not reachable from outside.

Verified that the host resolves on my mobile on 4G.

debug log:

18:28:58.195 DEBUG- create
18:28:58.237 DEBUG- GET https://acme-v02.api.letsencrypt.org/directory
18:35:32.792 DEBUG- Error resolving url. No path found. GET : /recordings/
18:35:32.792 DEBUG- Error resolving url. No path found. GET : /a2billing/admin/Public/PP_error.php?c=accessdenied
18:35:34.833 DEBUG- Hardware not logged. /185.53.91.39:54972. Closing.
18:35:34.833 DEBUG- Hardware not logged. /185.53.91.39:54986. Closing.

What server version do you have?

0.41.2

installed Rpi from scratch today.