Symptom
After updating to WHMCS 8.4.0, you may observe one of the following Exception thrown in jobs queue execution errors in the System Log:
Exception thrown in jobs queue execution (WHMCS\Module\Addon\Mailchimp\Mailchimp::createOrder) - Bad Request - We were unable to process the request. An order with the provided ID already exists in the account.
Exception thrown in jobs queue execution (WHMCS\Module\Addon\Mailchimp\Mailchimp::createCart) - Cart Already Exists - A cart with the provided ID already exists in the account.
Exception thrown in jobs queue execution (WHMCS\Module\Addon\Mailchimp\Mailchimp::updateCustomer) - Method Not Allowed - This list member cannot be removed. Can not archive a contact that is bounced, pending or archived.Solution
Apply the 8.4.1 Maintenance Release via the Utilities > Update WHMCS page.
HotFix
We have created a hotfix for 8.4.0 only to correct this behavior:
https://whmcs.community/files/file/175-addon-6138-exception-thrown-in-jobs-queue-execution/
