Hi, I just installed 4.0 payplans on a 3.9J! website.
When I proceed to checkout from this URL,
https://www.alumni-ensta-bretagne.fr/index.php?option=com_payplans&view=checkout&invoice_key=8O56WJCM559N&tmpl=component
I get an error message stating
0
ERREUR: 0
Serialization of 'Closure' is not allowed