Do you have a screenshot of the abandoned checkouts from these 36 attempted orders? You can send out abandoned cart checkout links so those customers can attempt to complete their transaction, or give you insight into what they are seeing on their end regarding the checkout process.
If there is anything else I can help you with, please let me know.
Thanks for the context. I'd recommend having them send you screenshots of the error they are getting on their end to isolate any potential causes. Feel free to share them here and we can go from there.