From the Excel help:
Requirements for merging Both workbooks must meet the following
requirements:
a.. Be copies of the same workbook, which must have been a shared
workbook.
b.. Have different file names.
c.. Either not have passwords, or both have the same password.
d.. Have change tracking in effect continuously from when the copies were
made.
e.. Keep change history back at least as far as the date when the copies
were made.
For example, if the change history is being kept in the workbooks for 30
days, and the copies were made 45 days ago, you can no longer merge the
workbooks.
Plan ahead for later merging When you turn on change tracking but aren't
sure when you'll merge the workbooks, set a large number of days for the
history, up to the maximum of 32,767 days.
Merge changes manually If the workbooks still won't merge, you can
incorporate the information from one workbook into another manually, by
copying and pasting from one workbook to another.
Regards
Dave
