We've been using the Mitel 5624s with our Meraki wireless for a year or so now.  We've changed a couple units and everything goes fine.  The one thing that we MUST do is set the 802.11 protocol to only B/G for them to connect.  
We just purchased a 5634, but can't get it to connect.  There's no 802.11 option in these, only the band settings.
Anyone else have this issue and find a solution for it?  Another thing to note, i don't use a dock to program, just use the Admin panel on the phone itself.
Thanks!