Error during automated certificate renewal

Over the past 2 night we received these error messages:

New Message: Error during automated certificate renewal

Setting up certificate for a hostname: serveame.domainname.nl
Getting challenge for serveame.domainname.nl from acme-server...
Waiting for domain verification...
Challenge is invalid. Details: Invalid response from http://serveame.domainname.nl/.wel...yxR29sYBy5Wuo: . Exiting...

I've searched the forum but the solutions are at least 1+year old, so i guess outdated.

The server runs on the latest version of DA and Letsencrypt. Updated both yesterday, received this error message again last night.

Any ideas?