Can't sync local files from laptop to iPhone

[K_Tsang]

Recently, I just can't sync the local files between my laptop and iPhone...

I'm really frustrated and looked up here for help. The other said they solved it by reinstalling the app, I tried and it's worse now. The old songs which were successfully synced after re-launching the app they all become inaccessible. Cannot be played on my phone which I have enough storage around 8GB and only 20 songs to be downloaded not exceeding the limit.

I just can't sync like the way before, does this only happen to me or it's due to the software bugs or upgrade problem? Please help me out coz otherwise I may switch to Apple music which it's the worst solution... Anyway, thanks!