Urgent: Unable to Create Seller Account on Mercari For Testing My Code

Hi so I'm based in the UK and need to test my code but it won't let me sign up. I did get someone's help in the US to create an account for me but still can't sign in - though they can sign in fine in the US.

So, how do I bypass the geo-location restriction? I have used vpn, location spoofing and other things, still can't sign in.

Please help!