Get someone to press the starter button whilst you put your ear close to the starter motor. If there is a distinct click then the solenoid should be OK. If there is absolutely nothing – very unlikely – then before doing anything drastic I’d advise trying a new start battery – even a cheap car one in the first instance.
If the solenoid does click then is probably just that the starter has seized. If so it is unlikely to be a serious problem. Try to turn the engine over by hand or with a big spanner to ease things.
But try a new battery first. Starting batteries do not like being left unused and uncharged for any length of time, especially not in the cold.
