Troubleshooting Clients Unable to Login
The error Login Details Incorrect. Please try again. error may occur when logging in as a Client with known working details.
The most common cause of this error indicates a System URL mismatch. This often occurs when first installing an SSL certificate onto your WHMCS instance after not previously having one, or forgetting to update your System URL after moving your WHMCS to a new domain or directory.
To resolve this issue, check to ensure that the WHMCS System URL setting is correct in the General tab at Configuration > System Settings > General Settings.
For steps to check and update the system URL, see Updating the System URL.
After you update the system URL, attempt to log in to the Client Area again.