I’m assuming this worked before but to double-check what is the thermostats FW Version? Needs to be 1.50+ in order to be always on.
Assuming its at or higher than 1.50 the next thing would be to remove the TSTAT from the back plate, remove the batteries and leave it off for 2+ minutes. You will want to verify that the C-Wire is firmly attached. You will want to turn off power to the TSTAT before checking C-Wire connection.
If possible, check C-Wire for voltage with a multimeter.
If C-Wire is firmly attached and has voltage, the next step would be to:
Remove the TSTAT from the Z-Wave Network
Factory Reset the TSTAT
Add the TSTAT back to the Z-Wave Network.
Reprogram TSTAT function through Alarm.com (including Display On).
Test for resolution.
Even though you are not working with programming the panels security functions. when troubleshooting, you may want to place your 24/7 professional monitoring account on Test Mode during troubleshooting to avoid any false dispatches.
You can do this by calling monitoring operators directly at 855-348-0367 or from the Test My System tab in the System Manager section of your Surety account.