I'm trying to enter the requested information for a new build of an app, but the system doesn't recognize a valid phone number :-( Every help is appreciated Peter

Hi *, I'm trying to add a build for external testers. Everything work fine up to the point where I have to provide the information about the contact person. Entring the phone number always results in an error message that the phone number can only consits of numbers (what it really does). Has anyone a hint how to fix this problem? Peter