A month is too long a wait.
I'd first do a whois check of the domain to see if the previous owner has already pushed the domain to Sedo.
If pushed, then the problem is with Sedo service rep and you just need to 'remind' him to send it to you...your deal will go thru sooner or later.
If not pushed, then probably the problem is with the seller. You may want to 'push' Sedo to get an answer from the seller, or demand money back from Sedo.
