Go into the Blocks palette and open the Block (EC button).
Select the object using the "Edit Facet" tool.
Select a facet, then Ctrl+A to select all the facets.
Go to Properties and choose a different Category.
Leave "Material" at "None".
You should now be able to select the object and change its material in the normal manner. "Finish Edit Content" to the Block.
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John R.
V17—V21, 2015—2019
Designer, Deluxe, (Professional, Expert, Basic), Platinum
RedSDK enabled
Windows 10 Pro (1903), 64-bit