Anyone advising specific actions to take in this thread that aren't "get a lawyer, preferably an expert in this field, and follow their advice" is doing you a disservice. This is almost certainly something you can't DIY. If the monetary amounts are too small to be worth a lawyer, you have very limited options.
Get. A. Lawyer.
I'm guessing you're breaking a rule and their banking partner is unhappy with whatever business you're in. If that's the case, then Stripe's hands are tied and your fate is sealed.
> but the account was still closed and Stripe is about to make a mandatory refund of all funds in the account (including the actual purchase price of the product).
I'm no expert but this sounds like a claw back, or some liability shit. A good reason to not keep money in your receiving account. How big are your transactions? Refunding everything going back how long?
You've painted only a small part of the picture. Without more, I'm not convinced this is good faith. I've seen too many shady businesses pull the same tactics.
Usually but not always it is a division underneath the Department of State; for instance in Colorado I think it is this group: https://banking.colorado.gov/industry/money-transmitters .
If you don't feel that Stripe is treating you fairly, you should get the relevant agency involved...
(EDIT to add: yes, you should get a lawyer involved also...)
I'm surprised I've never seen such a system since, it seems very effective against stolen cards.
There are many competitors in this field and the companies that do this for a living operate a much better service than Stripe. Some of them will even fully refund false negatives if they are later disputed.
I was involved in cutting Stripe Radar and moving to one of their competitors.
Unfortunately, as a small business, you are a target for "carders" and other criminal figures.
I'm not sure why anyone would keep money in Paypal or Stripe.
1.) Those without checks who take everyone but later will easily bann/block accounts.
2.) And those who are more restrictive to take on customers but will work with you instead of blocking your account.
Everyone needs to chose their preferred payment provider, you usually can't have both.