When adding device back to HomeKit, keep getting “the setup code is invalid”

I set up a new network at home and had to remove a gateway from HomeKit (or whatever it’s called) so I could reconfigure it for the new network. After joining the gateway to the network, I tried to add it to HomeKit. When I try to add the accessory, I choose more options and see the gateway listed. I then try to manually enter the setup code and get the error. I’ve tried updating all Apple products and the gateway previously worked on HomeKit, but I have no idea what to try next.