Hi Michael,
I looked at your data, and for some reason, the latest version of your Truck assembly has zero references to any other files!! I don't know how this could have happened. It is possible there was a problem downloading anything other than the top assembly, and the assembly opened with unresolved references. You should've received an error message when that happened, and it would've warned you that saving the assembly in this state would result in the file losing all references. I can dig a bit deeper if you can send me the diagnostic log files. The location of the diagnostics file should be shown after you run the Gather Diagnostics command.
The good news is that you can "promote" the previous version of the Truck assembly, and it does seem to have all the references intact. I hope you can reuse the previous version and redo your steps on top of it.
Regret the inconvenience. Would love to identify the root issue. But will need the log files for that.
Regards,
Ahsan
Ahsan Ali
Fusion Senior Software Architect