If a payment processor suspects a business is laundering money, they can hold the funds, but it's illegal for the payment processor to tell the business that they suspect money laundering. So they end up saying something like "we're holding your funds for vague unspecified reasons".
(Disclaimer: Used to work at Stripe, but not on this particular area. Not an expert on either the law or Stripe's policies.)
ETA: Maybe it's more that they can't give you any information because they can't allow adversaries to differentiate between glitches, random screenings, and investigations?