Replaced battery a few weeks ago, now will not charge.

Have you tried a different charging adapter?

Just because the connections look fine doesn't mean they are fine. The MagSafe connectors are magnetized; there can be metallic debris stuck on the connectors. There can also be nonmetallic dirt/grease etc. on the connectors, and it may interfere with the electrical connection. It's also possible that the pins on the MagSafe connector may be bent, and aren't connecting cleanly with the charge points on the computer. And of course, the cable connecting the MagSafe connector to the power block is very thin and very fragile.

Apple has a tech note on MagSafe troubleshooting:

https://support.apple.com/en-us/HT203207