Dead battery my guess, but why guess?
Take the guess out of batteries and get one of these. ANCEL BTS200 battery analyzer. It will tell the condition of the battery you don’t have to mechanical have knowledge it tells you if it good or bad.
Amazon.com: ANCEL BST200 Battery Tester 12V Automotive, Car Battery Tester 100-1100 CCA Battery Load Tester Tool Digital Analyzer for Car Truck Motorcycle SUV Boat and More : Automotive
Or similar and shop around can be as low as 30 bucks.
Takes all the guessing out of condition of battery.