Autocad will usually give you hints on why the Xref won't bind.
If you give us the error message you get, that may help solve the problem.
Also, try some of the following to fix the problem...
-use the tree view in the ‘Xref’ manager to see the locations of the problem xref and in which drawings it occurs.
-bind individual xrefs one at a time, to isolate the problem drawing.
-try purging and auditing both the xref source and destination drawings.
-you may have to ‘wblock’ the whole ‘Xref’ source drawing to another file then erase the original ‘Xref’ file and rename the new file.
I have a few more tricks, but hopefully yo will solve the problem before then
Hope they help!