Myob Teams App won't accept new employee.

I have a new employee who has been invited to the Teams App, he has tried numerous times to get it working from the invite link but it comes up with an error.  I have deleted him and reinvited him so many times I've lost count, he has uninstalled it and reinstalled it just as many times with no luck, he has checked his phone's iOS is up to date.  There are no help topics for this in the support pages that I can find, I just go round in circles with no information or help on this at all.  I can't even find any support contact information.

Who do we contact for help with this please.

Rae