roundcube can't add contacts

yesterday a client spoke to me about not being able to add contacts to his roundcube account.

he showed it to me what he tried and he got after “adding” the contact a general error.
I tried to locate the error log, but I couldn’t find anything roundcube related.

When this client was running on my directadmin server he had no problem at all with roundcube, but now running on interworx he has this problem…

could somebody here help me with this?

Best thing to do would be to open a support ticket so we can get in there and take a look: