Clicking sounds, when they happen in your car, often mean the battery voltage has fallen. Often, but not always--there are, regrettably, other things that can be causing it, but this is one you can check at home.

If you have a voltage tester, check the voltage of your battery. Any battery left sit since July has a good chance of self-discharge.

A "12 volt" battery has a wide range. If it's reading 12 volts, that's actually not good. A live battery should be reading much higher, around 12.6 volts in a good charge state.

(A bit of spot research indicates that the Craftsman does use the 12 V battery, but absolutely check your manual before continuing from this point)

You might be able to jump start the battery from your car, but again, check the manual. If not, a 12 V charger may have a 50A setting that will allow a jump start from house power (mine does).

Post that, running the mower should recharge the battery if it has an alternator. If not, it will need to be recharged. You should use a safe and reliable 12 V battery charger to do this. I use a 10 A automatic adjusting model to charge my car right now during the pandemic since I'm not traveling and do almost everything via audio or video call.

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Check the connections to assure that they're firmly attached as well. Sitting around can lead to a bit of warming and cooling and detach or weaken connections on wires. It's not likely, but it can happen. Make sure to wear electrically neutral gloves when fiddling around battery wires. They not only bite, they can kill if you complete a circuit across your chest.

The starter might also be a problem, but with it setting since July, my dollar's on the battery. Lead batteries don't reward sitting around very well. And I doubt it would have up and gone, and with sitting around, you threw a red flag on battery issues, so...

I agree with everything Morpheuspa has suggested , some other advice is to have your battery charged by a competent person and then load tested to ensure all cells are adequate . Often a weak cell will cause issues . Also once you get the tractor running ensure you are getting around 12.8 to 13.3 volts to the battery from the charging system .

Totally agreed with the above. (It's like an agree-fest here today). Even though a battery that's been stored can be expected to run down, it's never a bad idea to have a professional recharge and check it.