For clarity, you mean you can't get the player to spawn at said spawnpoint, defined by grouping? I actually have just touched on dynamic spawnpoints for an addon I am working on and by using grouping everything has worked as expected for me. They are altered at runtime so they can be used for "objective" spawnpoints etc. Like in battlefield if your team owns a flag in conquest, you can spawn at a location at close to the flag. I will be expanding this for squad spawning also, so you can spawn of a squad member if they are alive.
The position and rotation you feed in do not seem to matter. They come back altered (ref), and that seems to be all, I don't think what you feed in is actually accounted for along the way, but I have not dug into it. I simply tried by position first assuming I may be able to define a location and then the spawnmanager would choose a valid spawnpoint closest to that selected location. This did not work as I expected it would so I did not bother going that route. Instead I stuck with the spawn grouping and modify on the fly, which seems to be working great so far and with enough spawnpoints I can see spawn killing being eliminated (I did some quick tests on this).
In saying that if we could use position to also influence the returned spawnpoint, that would be awesome!
-1 should ignore grouping, so forget using that for any chosen spawnpoints.
I have not tested without obstruction check.
Make sure your obstruction layers are correct, avoid having "Default" included.
Make sure respawner component has same grouping as the spawnpoints you wish to spawn at, which you obviously did. I do this by code, which maybe the only difference, so unsure if changing in inspector has the same result (possible inspector bug?).
I have successfully spawned in 4 teams at 4 different groupings like this. And the amount of teams can be unlimited really.