Hi. I just solved this issue in my phone. Also, I found a way to play music even when the app wouldn't connect to mobile data. Sharing my experience below -
I had been facing the same issue for days. Spotify worked on Wi-Fi but it just wouldn't connect to my mobile data (Vodafone). [Although I should mention that it WOULD sometimes randomly work on mobile data but that was very very rare and temporary]
I tried **bleep**ing everything -> re-installing, turning on data access, deleting cache, rebooting, turning off voice over LTE, ensured my mobile was running on the latest software update, allowed all app permissions and God knows what else.
Now, after many a frustrating days, I did these two things simultaneously and one of them worked for me. Idk which.
1) I put it on and off airplane mode once
2) Disabled the 'Always-on VPN' setting in my VPN app (SuperVPN).
Somehow even if you closed the app, the VPN stayed connected. I didn't notice this because the VPN symbol would also disappear when I closed the app so I would assume it isn't connected. But when I opened the general phone settings and checked the VPN option, it showed that the VPN is still connected. And this happened because the 'Always-on VPN' feature was enabled in my VPN app. Here's how to disable it (in my MIUI phone) -
Settings —> VPN —> settings of the VPN app installed —> disable 'Always-on VPN'
Attaching screenshots with this if possible. Between the airplane mode and the VPN I guess it was the VPN that worked for me but I'm not too sure.
OK, I was pretty lucky to get my Spotify working again but after days of tinkering around I had almost given up and accepted it as the new normal. Resorted to using **bleep**ing YouTube when outside. 🤦♂️
HOWEVER, I FOUND A WAY TO PLAY MUSIC EVEN WHEN IT WOULDN'T CONNECT TO MOBILE DATA. Here's how -
When I would open my playlists, I couldn't play individual songs because obviously it wouldn't **bleep**ing connect to mobile data. BUT, if you hit 'Play' for the entire playlist, it will randomly play a song from it and if you then open the 'Que' you'll see all the songs from the playlist queued up randomly and now you can individually select a song from this 'que' and play it. Or you can just re-arrange the songs as per your liking.
So, technically you can still play songs but you gotta hit play for the entire playlist first and then choose the songs from the que.
Now, all of this worked for ME. I'm not sure if it'll work for you but you can certainly give it a try and let me know if it worked.
If my experience is helpful to even one equally frustrated poor music-loving bloke , then it will have been worth it. And it better be!! coz I had to faced some some really agonising and frustrating music-less days and also had to specially make a community account just to be able to type all of this out 😤