Not able to enable external testing of my app due to phone number validation. The error reports "Make sure the contact phone number only contains numbers and try again.". Attached is a dummy phone number with the same validation result.
I had the same error. But the solution is simple. Lets say, my phone number would be (because I'm a German) +49123...
Don't follow the: "Only enter numbers" error, but instead, enter:
+49 123 1234...
But important: with the extra spaces between the different parts of your number.
Entering for example 0123456... (as it is usual for at least European numbers) wouldn't work.