Perhaps since Fences 6 is using newer layout engine. But, first try the restore the old saved layout snapshots, if that don't work, most probably, you will need to manually rearrange all the icons back into its designated layout.
Also, it is recommended to use the "Store my layout on a per-monitor-configuration basis" refer screenshot below. Do this first before manually rearrange all your icons.

Thank you,
Basj,
Stardock Community Assistant