We need to get the secret key from WHMCS module configuration.
Option 1: Check WHMCS admin panel → Setup → Payments → Payment Gateways → Cashapp Payment → Callback Key
Option 2: Update the database with the correct secret key manually
Test Values:
Calculated Hash: 4dc82047215bf32fd8658598e4fe21a8
Note: This hash should match the one sent in the callback POST data.