Starter not working?

The car had been sitting for 8 years and decided to get it starting. I first started by changing the battery and giving it fresh gas. That seemed to do the trick because after a three or four cranks it started right up. Now a couple of weeks later it won’t start. I’ve just put the battery on a tender and looking for what wrong. Also when it was started I tried moving the car and put it gear and it wouldn’t move wondering if the transmission was bad or it just needed fluid? Because I check all the fluid and top them off.