Here's how I'd approach it.
1. Make sure you have 12+ volts at the battery terminals. If not, correct the problem. If you recently connected the battery terminals, make sure you did not reverse them when you reconnected. If the polarity is reversed, the detector will not function.
2. Access the fuse/circuit breaker panel. Check each of the 12V spade fuses and make sure they are not open. Replace if bad.
3. Pull the detector from the cabinet and use a DVM to check for 12V at the input wires. If no voltage, trace the wires and determine if there is an in-line fuse that has opened. If so, replace it.
4. If you have 12V at the detector and it's still not functioning, contact
Safe-T-Alert at 1-800-383-0269.
Here is the operating manual for the detector:
Safe-T-Alert ManualJim