I’m not anyone official (just a Pro user), but I noticed in your error message the problem is related to the Stripe payment service (back-end purchases processor for Mailspring). It is pointing to here:
This page advises that Stripe cannot process your payment because your particular credit card or payment method is requiring additional authentication (such as a bank login) before it can move forward. There are likely only 2 fixes:
Wait until someone from Mailspring Staff adds some additional error-handling to the payment system/flow to let you “authenticate” further during the payment process.
You might be able to work-around this by trying a different payment method or adjusting your security settings with your bank (but that might not be desirable for other reasons, obviously).