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First, as a test, disable the Vanish featureQuick-hide feature:
In Fences 5, this feature can be found under the “Hide” tab of your Fences Configuration application:
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Other versions of Fences may have the quick-hide setting located under the “Vanish” or “Quick-hide” tab:
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If this does not help, please make sure you have not inadvertently put the Fence on an alternate “desktop page” using Pages. Disable Ensure Pages is disabled to see if the Fence \ Icon is returned returns to your main desktop:
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Automatic Layout
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Then restore a recent Fences layout Backup/Snapshot:
https://support.stardock.com/space/SHC/1331331082/How+do+I+use+snapshots+in+Fences