Downloaded Playlists not updating with new songs

I have a playlist downloaded on my Iphone that won’t update automatically or manually. I also have a list of albums and artists I have downloaded.

Downloads: 1443 Tracks 12Gb of which my playlist is 5.9Gb.

Is there a limit to the amount of songs in a playlist?
Is there a limit to the amount of storage PlexAmp can handle?

I still have over 20Gb of free space on my phone.

shouldn’t be, besides the 24 hour limit on each downloaded item, which you might be running into?