Join-script error after installing Wordpress

[tpfann]

while investigating for EXITCODE=51 I came across this posting:

Next Cloud failing to Join

Hello, I am running Univention Coporate Server and wanted to install Next Cloud. Installation goes through but when i try and log in it says wrong username and/or password. I have ticked two user accounts to enable NextCloud but still cannot log in. If i go domain join i can see 50nextcloud in pending state. If i run the script it says it fails. In join.log i see the following -: curl failed with error 51 EXITCODE=51 Fri 22 Dec 08:29:44 GMT 2017 univention-run-join-scripts finished I …

As I’m using a LetsEncrypt certificate as well, I’m wondering if the root cause for my issues could be the same as described in the above post. How can I find out?