Can't comment on why the other things weren't enough, but do you have a "real" phone number or is it VoIP? I was unable to verify my Twitter account until I contacted support, nor could I get the IRS website to take my number when doing taxes, and I think the reason is that my (small) carrier uses VoIP: https://help.republicwireless.com/hc/en-us/articles/36002509...
