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Honeywell L7224U issue

I have a crown bd-74 boiler. Early in 2016 I replaced the aquastat with the L7224U and I've had no problems until now. My boiler is running at about 120deg. It is cycling on and off, and it is maintaining my home about about 63degF, regardless of how high I turn my thermostat. The display on the aquastat is showing STA 1. There are no error codes. This issue started a couple of days ago. Can someone tell me what this code means, and where to start troubleshooting? Thank you.