Error in Let`s Encrypt

Hi,
ich have a problem…
Obtaining a new certificate
Performing the following challenges:
http-01 challenge for meet. 8punkt6. de
Using the webroot path /usr/share/jitsi-meet for all unmatched domains.
Waiting for verification…
Challenge failed for domain meet. 8punkt6. de
http-01 challenge for meet. 8punkt6. de
Cleaning up challenges
Some challenges have failed.

IMPORTANT NOTES:

Is port 80 open (and properly forwarded, if behind a NAT)?

yes, see it on http://meet.8punkt6.de

Shouldn’t you be getting a cert for this instead?

linux2004.cw2lgs673ap23ze0.myfritz.net/

hmmm… linux2004.cw2lgs673ap23ze0.myfritz.net/ this is the dyndns from my router forwarded to the linux machine
when i use https://meet.8punkt6.de ERR_SSL_PROTOCOL_ERROR
i think i need the LetsEncr. on the linux machine?!