Landing a sale depends on your offer, how attractive it is to the potential customer, what benefits your offer to your audience etc. If you can find a seller that has an audience that matches what you offer, you will get much better results.
Please note that most of the sales come from follow-up messages. Try to build a list by setting an opt-in page as your landing page to collect opt-in first and your sales page as a thank you page. Most people decide to buy after 4-5 exposures, and most sales come from follow-up sequences.
And I am not sure why your funnel doesn't work on this platform. I'd suggest contacting the customer support of Udimi to get better assistance.