AutoSSL not working, ipv6 address not resolving

Dear community, after fighting for ages with this error, I urgently seek your friendly support. I've set up a website for a friend, using Bluehost and wordpress. But something went wrong so that AutoSSL always throws me this error: REDACTED I'm not too much of an expert (gosh, I'm a noob, and I'm lost af..), but I tried to dig down the hole a bit, and I was wondering if the problem lies here: * Before using "bluehost", my friend has had a contract with the domain provider "IONOS", and the ipv6-address above still points to some IONOS-server, instead of bluehost.. * When I'm logged in on "bluehost", it states that the domain has not been fully "transferred", so it lies around somewhere at IONOS. When I click on "Transfer To Bluehost" in the "Domains"-section at bluehost, it answers me to "Please enter a valid domain name. We currently only support the following extensions com, co, org, net, us, info, biz." So there seems to be no way to migrate/transfer this .DE-domain to bluehost. The contract with IONOS ended some days ago, but IONOS somehow still seems to hold/block the ipv6 address..? So my questions are: a) Is this indeed the problem that keeps AutoSSL failing? b) How can I fix this? Thank you SOOO much for every single piece of help here! :)