issues with employees and the myob teams app

Hi Myob Community, I have a similar issue with a member of staff.  He can log on to his Team and can start work but when he clicks it off his screen IPhone it logs him out and then he has to physically re input his email and passwork, every time.  It has been doing this for two weeks since he moved house.  I have tried getting him to delete the app and reinstalling it and that did not work. I have also tried deleting him from my team and reinstalling him and all that did was lose his hours he had worked for this week :(  Prior to this he did not have a problem with it and he was one of my staff who taught others how to use it on their phones so he is techsavy.  Could it have anything to do with his recent move of house, he has changed his home wifi system and he is not in a particularly good wifi zone but he is still managing to get wifi on his phone???