Summary
On a computer containing Plato and ArtiosCAD, upgraded only Plato from version 18 to version 20 and did not install CADx. Also did not upgrade ArtiosCAD to version 20.
Symptoms
Plato launched, but eventually opens after five minutes. Opening existing files take about two to three minutes. "CADx not installed" error message appears.
Solution
Upgrade ArtiosCAD to version 20. ArtiosCAD and Plato must be on the same version.