In this situation, it's best to determine the cause of the problem before deciding on the best course of action. The fact that the copy/monitor icon is not showing up and you did not receive the notice that the grids or elevations have changed location suggests that the link between the architectural and mechanical Revit files may have been lost or disrupted.
It's best to reach out to the architect again and ask if they are aware of any changes made to the architectural Revit file that could have affected the link. It's also possible that the link was accidentally broken or that the workset containing the grids and elevations was accidentally detached or deleted.
If the link is still intact and the problem is caused by a change in the architectural file, one option is to move the mechanical Revit file to the correct elevation and then re-establish the copy/monitor links on the existing grids and elevations. This would be the most efficient way to fix the problem, as it would allow you to keep the existing ducting, piping, and equipment in place.
If the link is broken or the workset containing the grids and elevations was accidentally detached or deleted, you will need to re-establish the link or recreate the workset and then re-establish the copy/monitor links on the existing grids and elevations.
On the other hand, if the link is lost, it's best to erase all the gridlines and elevations and start a new copy/monitor with new grids and elevations and re-link the files again.
In any case, it's important to communicate with the architect and make sure that the changes are intentional and that the link is properly established before making any changes to the model.
