If the internal RF chip has burnt out, it cannot send the "Ready" signal, resulting in the 004 error.

to allow the internal capacitors to discharge.

If the steps above don't work, you may be looking at a hardware failure.

Troubleshooting the RFN004 Error: A Complete Guide to Fixing Your Unit

Getting this fixed doesn't always require an expensive service call. Here is a step-by-step guide to troubleshooting and resolving the RFN004 error. What Does the RFN004 Code Mean?