Just encountered the same issue when registering multiple participants for an event. After filling in the card details and 'continue' the console logs this:
2020-01-07T17:38:18.103Z civicrm_stripe.js: clearing submitdontprocess civicrm_stripe.js:5872020-01-07T17:38:18.121Z civicrm_stripe.js: submit handler civicrm_stripe.js:5872020-01-07T17:38:18.152Z civicrm_stripe.js: Stripe is the selected payprocessor civicrm_stripe.js:5872020-01-07T17:38:18.153Z civicrm_stripe.js: We don't know the final price - registering additional participants civicrm_stripe.js:5872020-01-07T17:38:18.153Z civicrm_stripe.js: getTotalAmount: 0.00 civicrm_stripe.js:5872020-01-07T17:38:18.156Z civicrm_stripe.js: handle card payment civicrm_stripe.js:5872020-01-07T17:38:18.990Z civicrm_stripe.js: isRecur is false civicrm_stripe.js:5872020-01-07T17:38:18.990Z civicrm_stripe.js: We don't know the final price - registering additional participants civicrm_stripe.js:5872020-01-07T17:38:18.990Z civicrm_stripe.js: getTotalAmount: 0.00 civicrm_stripe.js:5872020-01-07T17:38:22.412Z civicrm_stripe.js: handleServerResponse civicrm_stripe.js:5872020-01-07T17:38:22.415Z civicrm_stripe.js: error: Invalid positive integer civicrm_stripe.js:587
Also, could I suggest changing the way the error is displayed - it's easy to miss it. A pop-up would work, or at least some red.
So if the them (eg. bootstrap) supports those classes it will be displayed in a big red box. PR welcome to add additional classes so it appears red in other themes too.
For the multiple participant issue I can see where the issue is - we're correctly detecting that it's a multiple participant registration but then trying to follow the standard stripe payment process instead of the alternative (which we use for recurring).
@mattwire The end user reports that they are now able to purchase multiple tickets. However one of the particpants had a new account created which then had to be manually merged.
@mikantchap Glad it is working! Account creation has nothing to do the Stripe extension - it will probably be related to your dedupe rules in CiviCRM. You should investigate why the new account was not matched to an existing one and then possibly open an issue on CiviCRM core if you think there is a bug.