key fob not working after disconnecting the battery?

So what sometimes happens is the connection at the battery can cause a voltage surge which can distract the protocol for the CAN bus system. I would do a hard system reboot to restart the systems from scratch. This guide can show you how:

https://www.2carpros.com/articles/step-by-step-guide-performing-a-hard-system-reboot-for-your-vehicles-electronics-systems

Please go over this guide and get back to us.

Hi Ken L.I tried all 3 methods and nothing. I have a 2014 Subaru Forester 2.5l .Thanks...

Okay, lets check the fuse #4 and #15 in the fuse panel. Here is a guide to help you and the fuse locations in the image below.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the images (below). Please let us know what happens.

Both fuses are good...

Okay, then it looks like the TPMS and keyless entry control module is out, here is the location so you can check it out. A CAN scan should help confirm it. It looks like it will need to be programmed in. Check out the images (below). Please let us know what happens.