Will the process create an Access format file as well as an Excel export file?
If so it sounds like something in the chain has changed.
Are you connecting to the Access DB via ODBC or OLEDB or some other method? Anything changed there - Database moved to a different place for example?
Has anyone made anything different for the database? Added or changed a password perhaps?
Any updates to the Access application made very recently?
I would have thought you should be getting some sort of warning or failure message somewhere - either directly form the process you are running a system "event" file.. If you can find those you may find a clue about what is going on.
Is it possible that for some reason the DB file has ended up in a locked state and so cannot be written to?
Sorry not to have anything specific for you but it sounds like one of those "guess in the dark until someone arrives with a flashlight" problems. It could have a number of causes.
the process will export data in excel and into a DB, however it will not export to any existing files. When I try to export into an existing file nothing populates and I get the -1. For example I created a new database using the current process and model, then tried to run again overwriting the table and nothing exports.