Hello,
I found the root cause of this problem and I think This should be raised in another topic for another plugin.
The root cause is that 2 firewall rules in the plugin “All in One WP Security” are creating this issue.
To avoid this error 403 to happen on stripe redirect after payment, Admin should unactivate bothe “6G and 5G Firewall Rules” in that plugin.
And all should work normally.