Vibration sensor v3 does not communicate with the gateway

Hello, a few months ago we acquired the Smart Industrial IoT Wireless Vibration Temperature Sensor and the NCD mqtt micro Gateway, we configured the Gateway and the sensor according to the NCD instructions (for this sensor it is very confusing because there is a lot of contradiction) and we could see the telemetry of the sensor in the Gateway configuration interface. After a couple of months the sensor batteries ran out (the sensor was configured to send the information every 15 min), the sensor was some weeks without batteries and after the replacement, our sensor did not communicate anymore with the Gateway, we tried to restore both the sensor and the Gateway and we were not successful. The sensor was left with the red led flashing (lights every 5 seconds) but the led lights with very little intensity (difficult to see when it lights), can you help me to solve the problem?

how many times the led is blinking ?

The red LED flashes once every 5 seconds constantly.