Re: Unrecognized database format
"Unrecognized database format" is commonly seen when the database has become corrupted.
First, copy your file to a work area. Then attempt to perform a Compact & Repair (C&R) operation on that copy. If it fails, you still have the original on which to try other stuff.
Second, how to prevent a recurrence? For that we would need to know more about the context of this database. Is it being shared among others? If so, has it been split or is it being shared as a single file? Or has it been split as a front-end (FE) and back-end (BE) pair of files? FE/BE splits help to reduce (not totally eliminate) corruption. We do not need to know about details of tables - but we do need to know about details of how the file or files are used.
Third, what was the cause? That depends on how you answer the second question, but the most common cause is failure to properly shut down the database such that something doesn't get correctly written back after having been modified. Things like rebooting a system with an open database, or powering off such a system, or (if network sharing is involved) losing network connectivity - all of these could do it.
In summary try a C&R to fix it for the moment. Then for diagnosis and prevention, tell us more about the database file or files from a structural viewpoint and from a usage overview.
I'm a certified grandpa (3 times now) and proud of it.
Retired over one year and survived being home all day with the wife. She must really love me.
If I have helped you, please either click the thanks or click the scales.