My 2018 Nissan rogue will not start and says key id incorrect. I've tried using the key fob end on the push button, but nothing. It will unlock and lock doors but won’t start the car. I did have a key programmer come out and program a new key, but for some reason his scanner cannot connect to the car. my guess it has to be in ignition. If someone can help me, that'll be great!

The scanner talks to the BCM during programming. The BCM needs power for that, and also to run the antennae that talk to the keys. So the first thing to do is check all the fuses and fusible links, both in the cabin and under the hood. The IPDM and Fuse&Relay Box are both on the left fender underneath the intake tube, so the tube has to come off to get at them.

I've already checked, but i can try again. Also, if the antennae is messed up thats on the roof, will that disrupt the car from starting? I'm thinking it works since the key is sending a signal because it does unlock and lock and opens the trunk.

No, the roof antenna is just for the radio. The main GHz antenna for the I-key is at the back of the center console, there are others in the cargo area and both front door handles at a minimum. Then there's a loop antenna around the button which uses an RFID reader completely separate from the GHz system, so the car can still be started if the fob battery is dead. If none of those work and the smithy couldn't communicate with the BCM, there are really only two choices, a power interruption to the BCM or the BCM itself is bad.

PS - I strongly suggest using a test lamp to check the fuses and not a visual check. Eyeballing tells you nothing about whether the fuse has power, only that it isn't blown. When you find fuses which are supposed to have battery power but don't, it will lead you upstream to the problem. There weren't any substantial changes to the Rogue power system between '16 and '18, so most or all of the PG section from the '16 FSM here in Nico should apply to your ride.
https://www.nicoclub.com/service-manual ... 6%2FPG.pdf

I did have another BCM from another 2018 nissan rogue that i put in there just to make sure it wasnt the BCM, but its worse cause the key won't unlock or lock the vehicle with the other BCM.

You can't swap BCM's like that, they aren't plug-and-play. That was a major mistake, now you'll have lockout codes in the ECM that won't go away until you get the thing talking and reregister the keys.

It wasn't only BCM, i did swap the ECM when i swapped with it. Also, for the ECM to work properly, would i take it somewhere to have it fixed?

No, once you get the keys to program then all the hardware should be on the same page and you can erase the codes in the ECM and BCM, including the lockout. Swapping the ECM and BCM together should have prevented any lasting problems, but unless you also had keys from the donor, both sets will now have security lockouts. You really need to find out why the BCM isn't talking, solve that and you'll get to the bottom of the problem. Swapping hardware isn't a good diagnostic answer.