Sensor Status is Unknown

deployed 1 base gateway , 1 wireless sensor hub and 9 wireless sensor (temperature and humidity). this same setup is deployed at 3 sites.

sensor status has a red exclaimmation mark and the name is tab shows unknown.

this is appearing for all the 3 sites.

Hi,
Please try to do a rescan and also check if batteries are good, also since it uses a 2.4GHz Zigbee, it should not be placed where there are 2.4GHz wifi near,
and also hub and sensor should have a clear line of sight