Hosting and let's encrypt - "Some challenges have failed"

Hello,
I have an error message during generating SSL cert with let's encrypt for domain in OVH.
I use for it external VPS, and for sure it works, I just created SSL cert for other domain (non OVH) but for OVH I receive error messages:

root@server:/opt/letsencrypt# ./letsencrypt-auto certonly --standalone -d pot.pl -d www.pot.pl
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator standalone, Installer None
Obtaining a new certificate
Performing the following challenges:
http-01 challenge for pot.pl
http-01 challenge for www.pot.pl
Waiting for verification...
Challenge failed for domain pot.pl
Challenge failed for domain www.pot.pl
http-01 challenge for pot.pl
http-01 challenge for www.pot.pl
Cleaning up challenges
Some challenges have failed.

IMPORTANT NOTES:
- The following errors were reported by the server:

Domain: portproinvest.pl
Type: unauthorized
Detail: The key authorization file from the server did not match
this challenge
"xxxxxxxxxxxxxxxxxx"
!=
"xxxxxxxxxxxxxxxxxx"

Domain: www.portproinvest.pl
Type: unauthorized
Detail: The key authorization file from the server did not match
this challenge
"xxxxxxxxxxxxxxxxxxxx"
!=
"xxxxxxxxxxxxxxxxxxxx"

To fix these errors, please make sure that your domain name was
entered correctly and the DNS A/AAAA record(s) for that domain
contain(s) the right IP address.