Having the exact same issue with a client 2018 QB desktop Pro.  I've been attempting to export a report to excel and get the message "excel could not open the data file".   Randomly, this started happening about 2 weeks ago.  I've run the update to no avail.

The CVS file will export which I can convert to excel but I don't understand why it's happening randomly.  Been using Excel with QB desktop for years.