Just FYI, My users have told me that they are annoyed with the strict phone number requirements... to the point that they would rather pick up the phone and call instead of using the form.
After trying a few myself, I see that any "readable" phone number seems to be rejected, even though they are all valid phone numbers:
1 234 567 8901 (not enough room to type it)
or 234 567 8901 (fits, but is rejected)
or (234) 567 8901 (cant even type it)
Hope this can be addressed in a future version.
Other than this, I have found this to be a very useful plugin!