I find that the library can be slow to load on both the iPhone, or iPad. Apple Music, or just the personal iTunes library. What usually helps for me is to one quit the music app by sliding up in the app switcher, and relaunching, or restarting the device and relaunching music. If that doesn't work, leaving the music app open and just letting the device sit for a few minutes also seems to work.. Hope you get it fixed soon.
Thanks, I appreciate the reply. Unfortunately I’ve been trying what you suggested for hours already. iOS only shows my purchased music and Apple Music albums I added this evening. No evidence of the rest.