SQL Restore Error: “Restore failed: System.Data.SqlClient.SqlError: The media set has 2 media families but only 1 are provided. All members must be provided.”

This error means that the original backup was done as a striped backup where the backup stream was split into two or more destination files.

When attempting to restore, you need to specify all of the same files. If the back up was split to 2 files, you must use 2 files to restore. The restore cannot be done from less than the full set of files used for the backup.