I have been facing this issue since a month. Many of my downloaded albums simply do not load in offline mode/ when without internet, and Spotify displays this message. I need to connect internet in order for it to show up again and then i can play the song without any issues.
I can search for the song individually from the album and then play it, but not through it’s album.
I have premium student subscription since 2 years and never faced this issue. I changed my phone 5 months ago, iPhone SE 2016 to an iPhone 15 Pro, so it makes no sense for it stop working, if anything, it should work even better. 
Downloaded content still works fine on my old device (iPhone SE).

I have tried literally every fix u can imagine. 
I tried redownloading all my music, cleared cache, i deleted and reinstalled the app, i logged out and logged in, i removed all other devices from my account, restarted my phone. Only thing left to do is remove my subscription. 
(My payment is complete if u are wondering) 
I’ve scoured the settings to see if anything’s disabled, nothing. I’ve searched for fixes on the internet, so far nothing has worked. I’m hoping i can find a solution here. 

(Update: Just again tried to find a song via search, it seems to have stopped working as well, most of my downloaded music doesn’t even show up in search now.)

Can’t open downloaded albums in offline mode