Invoice payment page: Error Unable to complete payment! Missing paymentIntentID.
Drupal 7.69 CiviCRM 5.19.4 Stripe 6.3.1 + MJW 0.6
It's a new install, and I've only tested with the test payment processor credentials.
I can make a test payment on the same contribution page when I don't reference an existing contribution.
I'd be happy to dig into some code if you provide some hints.
I was guessing that you've got a custom form field paymentIntentID that needs to be created/carried along somewhere, and for some reason your usual strategy doesn't work for some reason on invoice payment.
Note: an invoice payment page url is just a regular contribution page + &ccid=[contribution_id] added to the url.
I can try it using a real payment processor credentials if you think that might be the issue.