"Playlist no longer valid"

[Jumbles]

If I create a playlist using the Android app I can normally listen to it straight away but next time I try it tells me it's no longer valid. Also, it never shows up on the Desktop app. If I create one using the desktop app it's fine there and doesn't vanish but when it shows up on my phone it says it's no longer valid.

I can Like songs and albums and they show up in my Library on my phone. It's just the Playlists that are broken.

I'm using the free Premium trial so I don't know if that's the problem or if it's the Android app that's causing it. I've uninstalled and reinstalled, cleared the cache...

My phone is a Pixel 4a (Android 11)