Sometimes when your browser autofills the phone number, it enters it in an incorrect format and you see the error "Invalid phone number".
Solution:
- Delete all numbers in the phone number field and re-type it by hand (instead of allowing browser to auto populate it).
- You will notice that when you type it by hand it will automatically be formatted correctly.
- Then, hit your "tab" key and you should see the "Invalid phone number" error disappear.