My 2016 Ford Focus wouldn't start, so we jumped it and had the battery replaced. Pep Boys said it was corroded and definitely needed replaced. It ran for about a week, and wouldn't start again. My husband jumped it, it started, he drove it around, but when he tried to restart it, nothing. We just want to sell it at this point but I'd like it to run. What can be happening?
This sounds very much like the alternator is not charging the battery. A new fully charged battery would start the car quite a few times until flat, as you have experienced. Jump starting would then work, but the battery on the car is still flat, so it wouldn’t be able to start it again.
You need to get the alternator tested, since it could be faulty. It is also possible that there is a bad connection between the alternator and the battery, or even a blown high current fuse.