I am trying to use a RBSXTR that came with a R11e-4G routerboard in it and works fine. When I try to put a R11e-LTE6 routerboard in it, it keeps saying Functionality is minimum and will not keep the APN profile or any of the network settings I have in there.

I have attached the picture of where the error is occurring.

I hope I am not being dumb, but any help is appreciated.

Again: RouterOS and RouterBOOT version?

RouterOS version is 6.43.3. I have not had good enough connection to upgrade to latest 6.48.

I am not sure where to find RouterBOOT version.

Understand, but without connection you can not upgrade.
Probably on 6.43 newer products like LTE6 are unsupported.
Put back 4G and upgrade?

The connection is not good enough. I live in the USA and my company bought the wrong routerboard with it. To my understanding the R11e-4G uses bands 3, 7, 20, 31, 41n, 42, and 43. Only band 41 is used in the US as Sprint and I do not have that near me.

When I have the R11e-4g routerboard in it, it lets me choose LTE as the network mode and lets me put in my APN profile no problem. It also says "searching" as the registration status so I know its trying to connect, I just do not have band 41 near me.