I opened up one of our tank models and I can no longer modified it. Nozz. list as 3d objects and all data is there when I hover over nozz.
But I can not add nozz or edit existing nozz. The equipment pallet does not open when double click on equipment components.

Which version of the software is this ? 2020 or earlier ?

I once had this problem where I had created a model with Metric/Metric unit system. Then later when trying to edit I had a metric/inch system set and could not edit the model.

Setting it back to the correct unit system worked

found the issue. The x vertex for the model inadvertently was erased.
Restored a back up file.
thanks