DIAGNOSIS The Nest is in a safety lockout mode. It tried to turn on your heating system, didn't detect that it actually fired up, and is now waiting a long cooldown period before trying again to prevent damage. This is almost always a problem with your furnace itself, not the thermostat.
FIX Go directly to your furnace. 1) Check if the furnace's own control board has a blinking LED light. Count the blinks. 2) Consult the sticker inside the furnace door or for the fault code that blink pattern represents. Common culprits are a dirty flame sensor or a faulty pressure switch. 3) To reset the furnace and clear the Nest's "Delayed" message, you need to cut power to the furnace completely at its switch or breaker for about 30 seconds, then restore it.
IF THAT DIDN'T WORK If the furnace seems fine and starts right up if you bypass the Nest (by touching the R and W thermostat wires together briefly), then the issue is the Nest's 'W1' heating signal. The wire might be loose at the baseplate or at the furnace. Check both ends.
HEADS UP When you see "Delayed," the thermostat is basically telling you it's done its job and is now waiting on the equipment. Forcing it to try again by constantly adjusting the temperature won't help and can confuse the system. Address the furnace fault first.