Pairing the heat link wirelessly to the display may have failed, even with a wired connection.

It may pair wired but will not pair wirelessly or maybe not pair at all, with or without a wired connection. Here’s what to do:

• Find your heat link. Push and hold the button for 30 seconds until it turns pulsing blue. Wait ten seconds then reset it once more. 
• Get your heat link entry key. Found on your previous display: Settings> Technical Info> Heat Link> Entry Key (its 6 digits). With the cover removed find it on the left hand side below screw hole. Also printed on the outside of the heat link cover at the bottom.

• On your thermostat select try again, then try reset pairing, then try replace heat link. Enter the 6 digit entry key.

If this fails move the thermostat closer and repeat the process. Reset the display holding it in your hand pressing and holding for one minute. Then with a wired connection to the heat link try again.