Hi,
Thanks, that fragment already tells us two useful things.
For order 26911 the "endpage served" line shows the card page was built correctly on the server: a valid key (pk_live_, method_id 4), the additional data and the notify URL are all present. So HikaShop and the plugin are doing their part.
For the stuck order 26910 the only thing that reached the server is an empty notify (no paymentMethod, no token) and the order stays "created". That means no card was ever submitted from that browser, so no payment was taken. The problem is the Stripe card form not rendering in that customer's browser, which is what we suspected.
But the line that actually names the cause is not in what you pasted. The debug build arms a watchdog: 6 seconds after the page loads, if the Stripe form still has not rendered, it sends back everything we need (whether Stripe.js and the plugin JS loaded, whether they were blocked, any JS error, and the browser). In the log it should look like this:
... - stripeconnect
[diag] endpage form not rendered for order 26910: {"reason":"form_not_rendered", ... }
Could you search the payment log for that "form not rendered" line (or for "stripediag=1") for one of the stuck orders and paste it in full? Please also paste every [diag] line with that same order_id, from onAfterOrderConfirm down to the beacon, for a single order. That JSON is what tells us why the form did not appear.
If there is no "form not rendered" line at all for a stuck order, tell me, because that would mean even the watchdog script never ran, which is itself a strong clue.