I think I figured out another missing step in Tutorial 6 this time Getting started tutorial part 6: measuring sources — LSST Science Pipelines
After running the pipetask for #coadd_measurement, one needs to run #reprocessVisitImage before continuing with #forced_objects as shown in the tutorial, otherwise, it gives an error about missing PVI(s).
It looks like the original post here contains the solution, so I’ll mark this reply as the solution to point users to the original post.