NAV/APR Modes will not ARM

[BoeingDriver]

As the title states, I am unable to get NAV mode and APR mode to arm while in heading mode on an intercept course. When I select NAV, NAV mode engages right away. If it matters, I am also using the TDS GTN750.

Is anybody else having this issue in MSFS2024?

[fabristunt]

I have had this happen a few times, mostly with the Duke, but also with the TBM. I also use the TDS GTNxi.

It usually happens when doing multiple flights in the same session. If you do an RNAV approach on the first flight, then sometimes it will refuse to capture activate APR mode for the ILS/GPS on the subsequent flight.
However, I have not been able to recreate this intentionally.

[SadBucket]

No issues on my end, make sure you have the correct CDI source on the 750?... Very common mistake that I've seen in training irl.