I had tried it a couple ways, using load, not using load. I fell into the trap of trying more than one new thing at once, and switched over to TNManager.player.Get<>() for my gets, and sets, and I think that was where I went wrong. Those behave different than the TNManager.GetPlayerData() methods, and don't seem to force a save of the file.
I managed to get it all going now, but doing the TNManager.SetPlayerSave() then starting a coroutine to wait for that callback to come back, then looking for the player data I want, it seems to be working.
Thanks for the reply!