Thanks for your reply. Oh yeah, I forgot about that one.

Here are the errors in the sys_payments log:

Jun 09 12:24:57 [23] /m/payment/call/stripe_v3/get_session_recurring/7/ :

[stripe_v3] 

Create Session Error: `customer_update` can only be used with `customer`.

Jun 09 12:24:57 [23] /m/payment/call/stripe_v3/get_session_recurring/7/ :

[stripe_v3] 

array (

 'charge' => NULL,

 'code' => NULL,

 'decline_code' => NULL,

 'doc_url' => NULL,

 'message' => '`customer_update` can only be used with `customer`.',

 'param' => NULL,

 'payment_intent' => NULL,

 'payment_method' => NULL,

 'setup_intent' => NULL,

 'source' => NULL,

 'type' => 'invalid_request_error',

 'request_log_url' => 'https://dashboard.stripe.com/test/logs/req_xxxxxxxxxxxxxx?t=xxxxxxxxxx',

)