When i.dgn is opened in Navigator V8i SELECETSeries 6, the PS properties are not visible. this is because of Schemas for those ProStructures properties are not available in Navigator Schemas.
Attached are the schemas from ProStructures CONNECT Edition Update 3 which ned to be copied in specific location so that properties can be visible.
https://communities.bentley.com/cfs-file/__key/galleryfiles/00-00-27-58-97/CE-Update_2300_3-ECShemas.7z
The complete process is explained in the document.