Can you verify the thermostat has AC connected via the “C” terminal?
Not all devices are equal in terms of signalling. Door locks, for example, are notoriously bad at communicating over distances of 25+ feet. You typically will need a repeater or two for best performance unless within 25 feet.
Also, you absolutely have to learn in door locks and thermostats within 5-10 feet of the panel or you will likely run into problems. I recommend learning them in with the panel within just a few feet and leave it there a little longer after the panel registers the device type. On the other hand, light modules can sometimes be learned in 25 feet away or more. It is not recommended to do so, but the data being passed is minimal by comparison.
Construction of the home can also play a role. All in all it is always a good idea to have a repeater or two for devices more than 25 feet from the panel. (Light switches, plug in lamp modules, dedicated repeaters, and most thermostats learned in on AC will act as repeaters.)