I am trying to transfer the tablet to the Keep, but I can't. I've drawn the Keep symbol on the tablet as best as I can make it out, in fact, I was successful once at it (another game). But now the D'Nai just leave the tablet at the base of the pedestal. What am I missing?

The Bahro can be rather finicky, sometimes it takes several tries before the symbol you draw is recognized.

In which age are you? The icy one? If so, see Tahgira Keep Slate Symbol ?

hi steveacker!
I'm sorry about your problem and i think this is a bug because i saw it in some forum some time ago. But first, make sure that you take two steps away from slate after you drop it. Second, make sure you are not dropping your slate in the bubble as the Bahro can't go in it. If none of this works, most recommend deleting all the saved games after this problem began and to start from an earlier game. If this is your second time playing, i have learned that the files become corrupt and the game may need to be reinstalled.
Hope this helps! Good luck!

Make sure you're at least two clicks away from the Keep and make sure you're two clicks away from the slate where you leave it. The Bahro won't do it if it's one click outside the keep or if you are only one click away from the slate.