I've added a few songs to a public playlist on my PC. For some reason they are not visible in the playlist on my phone. I'm using a Huawei P9 with Android 7.0 with a premium account.
1. Add few songs on to the public playlist on PC;
2. Switch to listening on Andorid phone;
3. Go to the playlist;
4. Observe the new songs are not visible on the phone.