After updating to WHMCS 8.6.1, you may experience a TypeError error when the daily automation tasks are processing credit card payments via Stripe™ and a card is declined:

TypeError: array_merge(): Argument #2 must be of type array, string given in /path/to/whmcs/modules/gateways/stripe.php:0

Update to the WHMCS 8.7 release at Utilities > Update WHMCS.

We have created a hotfix for WHMCS 8.6.1 to resolve the error:

https://whmcs.community/files/file/183-module-7874-typeerror-in-processcreditcardpayments-task-with-stripe/