Premium, Android/Windows (trouble is related to syncing)

A very long time ago, I was getting a new phone, and I wanted to move my files over from my phone to my computer so I didn't lose them (I didn't have Spotify at the time). When I got Spotify, I realized I could put the files in playlists (as local files) so I could still listen to the same tunes while using Spotify.

Now, a WHILE after having used those local files on Spotify with no problem, I go to download some more files, because one of my favorite artists came out with a few new songs and I couldn't find them on Spotify.

So I downloaded them on my computer, and they play on the computer fine. But I also wanted the files to sync to my phone (which normally isn't a problem) when I find that all of the new songs are grayed out, and tapping on them doesn't do anything.

I looked this up, and it still doesn't work, so let me save you the trouble of asking:

--I logged back out and back in on both devices

--I'm on the same account on both devices

--I'm online in both devices

--Both devices are on the same network connection

--The file types are supported by Spotify. I can play the files on my computer perfectly fine.

--I have a Premium subscription, but I was able to sync my files in the past without one, so there shouldn't be a problem there.

--There is enough space on the device's memory

--I have the latest version of Spotify installed on both devices

--My device's firmware is up-to-date

--I don't even have 300 songs downloaded, and I only use 2 devices with it, so the 10,000 song and 5 device limit does not apply.

--My network is private

--Spotify is set as an exception in my firewalls.

--I reinstalled Spotify on both devices, and not only did this not work, it made it so that all of my PREVIOUSLY uploaded files were unusable on my phone.

--I tried making my phone a mobile hotspot and connecting my computer to it.