PJJ, the nest Heat Link uses a wireless “thread” to communicate with the Nest Thermostat. Typically the Heat Link is paired from the factory for European markets, and must be manually paired with Nest thermostat in US markets. The range for the wireless thread communicating is approximately a line of sight 350 feet, maximum. Have you tried bring the Heat Link itself close to the nest to see if they can see each other?
NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.
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