I have encountered the following problem. After calculating buckling modes I noticed that most of the modes are not available in the Viewer (I am only able to select the first two modes):
And for some reason the available results differ every time I perform calculations. For example I calculated the same model again without changing anything and this time none of the buckling modes were available in the viewer:
The Viewer considers a load case compatible if node deformation data is available for that load case. Maybe you can try deleting the *.sqlite file (the Viewer must be closed) and then re-open (in case of a syncing problem).