Hello,
Unfortunately, these are just notices but it gives an indication of what could be the problem.
Since the plugin is asking for the customer "sources" :
github.com/HikaShop/hikashoppayment-stri...ripe/stripe.php#L197
If the Stripe lib do not provide that information, the function which is called in the plugin will generate a fatal error (but since the code is in a "try/catch".. I don't know why that problem is not handle...).
github.com/HikaShop/hikashoppayment-stri...tripeObject.php#L137
But the real question is : Why does the customer do not have sources ?
It would mean that the stripe customer which is asked to the plugin do not exist.. Thing which is not managed by the plugin. It asks for a stripe customer and it should get a working result..
Did you touch your Stripe customer in your interface ? Did you test the plugin with new Joomla accounts ?
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.