Hi, I have the same problem.
Some years ago I had created a 000webhost account and park my domain into it.
Now, when I log into it, I don’t see my domain parked into my account, and when I try to park it, it says the this domain is already in use.
Any idea?
Your old and new emails are? 
Old domain is?
Alright, can you try parking now?
Now when I login says “internal error”
it is the same: ********************
It wasn’t the same. Domain gustavojacob.com was assigned to lg******mj@hotmail.com.
I have switched the domain owners. Please try parking it now.
Okay, never mind. The other account is from a friend of mine. I spoke with him and everything is good now.
Also, can you please remove my email from this conversation. I want it to keep private.
Thank you.
We’re glad the issue has been solved 