when I restore .prj files, some come up in the project manager as .dwg files. if you check the files using explorer they are listed as .dgn files. What can I do?
There is no column in the Project Manager that shows the file format or extension, so I'm curious where you are seeing the DWG listed in the Project Manager?
I would speculate that what is occurring is that you are restoring old prj Project backup files that originally came from the now discontinued Autocad based Promis.e version and those files were not properly migrated. Migration from the Acad version is a two step process and it begins in the old Acad version. As described in the Help files and in this wiki: https://communities.bentley.com/products/electrical___instrumentation/w/electrical_and_instrumentation__wiki/3597/moving-from-promis-e-for-autocad-to-promis-e-standalone
the migration process for moving a project from the Acad version into the MicroStation version is to first create a Project Backup file using the Project Manager in the old Acad version and at that time you must select the checkbox to save the prj file in MicroStation compatible format. Then when you use the Restore command in the MicroStationversion to restore that prj file, the files will finish being converted. My guess is that these files were backed up in the old version, but the checkbox was not set to save them in MicroStation format, so the migration is not completing properly and you are ending up with a bad result. I recommend that you restore the prj files in the original Acad version and make sure you are baking them up using the setting for MicroStation compatible format.
If you click on the thumbnails tab at the lower right side of the project manager screen, it will display the file. If it is working correctly you will see the drawing. If not, I see blank windows with no drawing, just dwg.
Yes, again, I would surmise that some prj files were backed up correctly in the older version using the check box setting and some were not. The ones that were not, are not working properly. You should try restoring the non-working files into the older Acad version again and backing them up again in that version, making sure to use the correct setting to save them as MicroStation compatible format.
My manager assured me that he did them correctly. I have no way of checking myself. I think that you may be correct though. I do not understand why looking at the drawings in explorer, it shows them as .dgn files?
Probably because the restore command tried to process the files, but was only partially successful. The format name was changed, but other supporting items did not get changed so what you have is not usable. It is relatively easy to rename a file extension, but that is no guarantee it is a working file or that it was truly converted.