As I can see final request to acme-v02.api.letsencrypt.org/acme/finalize/… is failed with 500 Internal Server Error and “Error finalizing order” message without any additional details.
I can confirm this is a bug on our side. In a nutshell one of your ACME account's authorizations managed to get into a stuck state. We're going to look at addressing the bug that caused this so it won't happen again but in the meantime I have some advice to get you "unstuck".
Do you know if its possible to create a new ACME account using DirectAdmin? If you can reset your Let's Encrypt state, create a new ACME account, and reissue your certificates with that account you should be able to continue without error.
You will also become automatically "unstuck" 2018-07-12 at 21:43:19 UTC but I think we can find a solution for you before then.
I see. Thank you. I’ll wait for your fix or for cert expiration on 2018-07-12 in worst case.
Currently I don’t know how to create a new ACME account using directadmin, so I’ll ask in forum.directadmin.com thread.
This is your ACME account key. If you move it out of this directory, DirectAdmin should regenerate it for you (by creating a new ACME account) next time you try to issue a certificate.