Why would my heat pump keep cutting off after 2 seconds?

Hi, We have an upstairs and downstairs unit. The upstairs unit is rarely used (mostly set to off) because we rarely use upstairs. I have recently encountered a problem with the upstairs unit and hoping to get some insight to it. No matter what the thermostat is set on (heat or cool) it cuts on for about 2... show more Hi, We have an upstairs and downstairs unit. The upstairs unit is rarely used (mostly set to off) because we rarely use upstairs. I have recently encountered a problem with the upstairs unit and hoping to get some insight to it.

No matter what the thermostat is set on (heat or cool) it cuts on for about 2 seconds and immediately cuts itself off. We have the same thermostat upstairs and downstairs so we took the front off the one upstairs and took it downstairs and it appears to work correctly on the one downstairs.

Any insight as to what is going on would be greatly appreciated. Thanks!
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