Help with links needed

I’m new to using a* pathfinding, and I’m having some trouble getting links between 2 gridgraphs to work. I’m making a top down strategy game. The game has both water and land, and most units can only travel one or the other of them. I have several grids made that I load from files at runtime. All that works well. But some units can travel both, and I want only a few places where they can cross over between them. I’ve created lnks in Unity’s design window. They are there, I can see them. Lol. But they are not working to allow movement across them. Every time I run they revert back to a high cost. I’m really not sure where I’m going wrong. Does anyone have any examples or code that would point me in the right direction? Any advice? I’ve been programming since the late 80’s, and I just killed 4 days trying everything I can think of, so I’ll bend my ego around about anything that might help! Any ideas on how to get 2 grids connected?