Bug confirmed in Windows FMP 12.0.4
This has been previously reported.
For More Information see: Display date values in Scatter Chart
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip