Troubleshooting a Module Not Found Error
Symptom
After applying the 7.8 update and placing an order via cart.php, the following Oops! error is displayed:
Error: Module Not Found

Navigating to the Setup > Payments > Payment Gateways page in the WHMCS admin area, will show an error:
The Payment Solution module could not be loaded, most likely because it has been removed. You should deactivate it now.
Cause
A payment gateway record is activated and configured, but the corresponding file is missing from the /modules/gateways directory.
Solution
There are two possible solutions:
1. Restore the missing module file to the /modules/gateways directory. You may need to upload the file to your server via SFTP or restore from a backup.
2. Deactivate the missing module, switching customers to a different payment gateway module in the process. Instructions for doing this are located in our documentation.