99 Legacy L 2.2 AT No Crank/no start

I've experienced intermittent no crank issues (turn the key multiple times before the starter engages) over the past few months and figured it was the starter giving up the ghost and decided to wait until it finally died completely before replacing it as this is not a primary daily driver. Fast forward to a few days ago. I had driven the car with no issues the day prior and went to use it again the next day. Turn the key with zero response, no click, no anything. Hooked it up to the charger figuring perhaps the old battery was flat. After 30 minutes on the charger I got a response to turning the key -- the starter whirring over but it did not engage to crank. Pulled the starter and had it tested and it passed 6 consecutive tests with no issue. Reinstalled and same response -- whirring but not engaging to crank. Any advice on where to proceed is appreciated.