I am sorry to hear you are having this behavior from your thermostat @Juliet1 and sorry for the late reply.
If you have not already check the breakers and switches at the location, to make sure nothing has tripped. Also check the boiler as it can sometimes have a separate switch on it. Confirm it has power, it should have a display or LED that turns on.
If it all looks good try and power cycle the Heat Link, if you're comfortable in doing so. Turn the power to the Heat Link off for a few minutes and then turn it back on. See if it has any reaction after when you press the button on it.
It's been a while since this thread was last updated so I'll go ahead and lock this thread. If you're still experiencing problems, please feel free to start a new thread and we'll be happy to help.