I have waited over a month (game time) after siding with Hardin and he has still not taken the Elder's seat. All I keep getting is "I am going to have my hands full, come back later" Anyone else have this issue or know why it hasn't updated?

It takes awhile, but it happens. Make sure you are waiting outside of the cell the Elder is in.

He's not sitting in a cell. He is still at his desk.