Please add the msfs-2020 or msfs-2024 tag to your post, depending on which sim your post is about.
Creating Flight Plans with Flight Planner and loading them to avionics through the EFB is a nice feature but it seems that not all planes support it. For instance, I have not been able to load a flight plan into a v35’s GNS 530 avionics or a 172 GNS 430.
Anyone knows if this is by design or is a bug? Is there any limitation on this feature?
Same here. They load into the EFB but not the GPS
I can’t tell you about the 172 but the V35 in MSFS2024 has the old, original and useless AS530 unit from MSFS2020.
You can’t programme it at all. When Working Title brought in their excellent GNS530 not all developers got round to retro fitting it to their previous releases (I’m looking at you Carenado) and in the case of the V35 Microsoft didn’t ask Carenado to fix it either. 
In 2020 Working Title also released a ‘redirect’ through the Marketplace. When installed this forced all those planes using the AS530 to use the GNS530.
We don’t have a Marketplace in 2024 and apparently WT won’t be releasing it in 2024 either.
We have to wait for the developers to update these models themselves…whilst those of us who want to use them in 2024 are left in limbo.
It’s a bit naughty if you ask me…
I’m having this issue again, this time with the Partenavia P68 Victor, that includes a GNS 430. Nemeth Designs says that his 430 is a standard one so I must think that the issue is not solved yet.
It’s a pity because the P68 is a mission-prepared aircraft but if the flight plan cannot be loaded then is completely useless in career mode.
You all might want to have a look here.
Some smart guys fixed a few planes.
https : / / flightsim.to / file / 90590 / garmin-navigation-suite-fixes
(Not allowed to post links, delete the spaces)
Or search on flightsim.to for Garmin Navigation Suite Fixes