i dont have anything to offer for your issues as I am having the same.
Trying to find the correct Classification for ceiling slabs so they map to the correct setting to Revit import sees them as ceilings.
Then how to get the grids from AC to be read in Revit? Use the Slab Accessories? I did that and still not reading the grid.
Here is a bump Jonathan.
Terrence Sturm, Architect
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MBP OSX 10.15.4 Quad Core Intel i7 2.2hz
AC 17 build 5019
AC 22 build 7000
AC 23 build
AC 24 build 5000