Same problem here. https://jira.secondlife.com/browse/VWR-27009
But, it's not absolute. Some of my older models are accepted with their custom physics shape, others are not. And all those models are in SL already, uploaded with the regular viewer.
So, I'm kinda confused on how to make physics shapes now, if almost half of them are not accepted, without telling me what requirements for physics shapes might have changed.
Also, all my physics shapes don't have material, they are mostly just a simple box. Models were made in blender and 3ds max.
So, feel free to vote on my jira thingy there, there's definitely something borked.