The 'modem not responding' error will be displayed if:
Step 1-Software Update: The software needs to be updated. Please download the latest software update package here - https://productsupport.em-trak.com/hc/en-gb/articles/28856175410973-PCN-63-A200-Software-update-Impaired-Radio
Step 2 - Terminate Unused Ports (RX wires only): The unused ports need to be terminated (this only applies if you're using the 14-way or 18-way cables). The ports can be terminated by adding 120 ohm resistors between the RXA and RXB wires, as per the recommendation in the user manual, or by installing the optional junction box.
Step 3 - Power Cable Only Test: If the error persists after following the steps above, disconnect all cables from the A200 and connect only the power cable to the back of the unit. Check whether the alarm remains active.
This will help determine whether there may be another issue with the unit.
If the alarm is still present, please contact our Support Team at support@em-trak.com for further assistance.