Tipalti Registration

Hi, I am having trouble registering for Tipalti so that I can be paid for work I have carried out over the last month. I received the registration link, but the 2FA will not work (despite the phone number I gave being correct). I have tried contacting the team several times and raised 2 support tickets but have yet to receive an acknowledgement or response. The first support ticket was raised 13 days ago. How do I escalate this issue for resolution?