Invalid phone number

About a month ago I was introduced to Drupal to help on an order system at my office. Bossman wanted users to add a phone number when creating user accounts. Got it setup and everything was working until I got a call from him today stating any phone number isn't accepted. Sadly since it's an order system a phone number is a requirement, but the only way to create a user is to remove the number altogether at this point. Here's a rundown on things I've tried...

"Phone Number" account settings only has "Required Field, Display on user registration form, Use parenthesis around area code" selected.

I've tried current accepted phone numbers to try and default to and update later, but regardless it gives me a "Value in phone number is not a valid phone number" error. 

I thought it might be permissions with a user creating an account being anon and not having the ability to, but even with an Admin creating a user we get the same error. Being such a beginner with Drupal I'm out of ideas on what I'm doing wrong or overlooking.