Their support is confused. Technically you don't even need a TD license to submit results (you can do it while still in the evaluation period).
Hate to pass the buck, but you should write to them and let them know you have a TD license, but you need a Hendon Mob access key in order to submit tournament results.
To be clear, I don't know how they hand out access keys ... if anyone can get one or if they only distribute them to specific venues. That's a question for them. But if you don't get back a satisfactory response, let me know and I'll try to get in touch with them to resolve it.