I think they disabled it deliberately because they’re implementing the VNAV feature.
For now you can’t use the APPR button for RNAV approach. Instead use the charts to position yourself to be at the right altitude and manually engage the Flight Path Angle descent at the right time to bring you down to the runway. When everything looks good, turn off AP for manual adjustment and flare.
I’ve done a few RNAV approaches in my YouTube videos and they’re generally okay.