ProTip :
A battery can still show proper voltage and be bad. They have cells in them, if one blows open then the battery becomes unserviceable. It can show proper voltage all day long, but the current needed isn't there.
Car lights come on, it'll show strong voltage...you're scratching your head thinking wtf is wrong? What gremlin took a deuce in my electrical?
Before wishing for a unicorn horn to touch and heal it, go snag another battery and pop it in. Dollars to donuts that this will solve it.
Happened to me twice, and a friend just 2 weeks ago in his new Nissan pickup. He argued with me right up until we got to Canadian Tire and have the battery tested. Said there should be a bulge, or acid coming out of the top, or some sign. Nope, battery looked new.