PrepSheet is run by one person, so there is no ticket queue and no support desk: messages go to the chef who builds the tools.
Email pacman@ascentterminal.com. It reaches the same person whether or not you have bought anything, and it is fine for questions about the free tools, the guides, corrections or the templates. An Etsy message to the shop at prepsheet.etsy.com works as well, and anything about a video can go in the comments on The Pass on YouTube.
Paid templates are sold through Etsy. For anything about an order, a download that will not open, or a file you cannot find, message the shop through Etsy at prepsheet.etsy.com. Etsy holds the order record, so that is the fastest route.
If a calculator or a template gives a result that does not match your own maths, send the inputs you used and the result you expected, by email or Etsy message. Formula errors get fixed, and the fix goes into the file for everyone.