The attribute table (VAT) of the input raster layer could not be accessed. It either is missing or may be corrupted.
You may have accidentally deleted or corrupted the attribute table under the raster dataset workspace. The attribute table can be rebuilt with the Build Raster Attribute Table tool. To avoid corrupting attribute tables in the future, do not edit them or manually delete them with File Explorer. Use the Delete Raster Attribute Table tool to remove them instead.