Local music flies won't play on iphone

[sllgatsby]

I have songs on my Windows computer that I have ripped from CDs and bought from iTunes. I can play them on the computer. But they show up as greyed out on my iphone. Here are the circumstances: 

--I have my computer and my iphone on the same internet connection.
--Computer and iphone are both are on, and both have Spotify open and active. 

--My device shows as connected to my account in Spotify. 

--I have added the folder than contains the songs to the list of Local files in Settings in Spotify on my computer. 
--I do not have more than 3,000 songs available offline. 

--I have added several local songs to a playlist that is available offline. This includes a song that I just bought and downloaded today from iTunes. I downloaded it both to my computer and my iphone. Also includes songs I ripped to the computer from my CD collection. 

--I have the current version of QuickTime on my computer, which is running Windows 10. 

--I have downloaded the codec that is suggested in the Spotify Help (13codecx). 
--If I open the "Local Files" default playlist on my phone, none of the songs I tried to play on my phone are listed there. 
--The songs show up in the available-offlline playlist that I added them to, but they are greyed out and cannot be played even when I'm connected to wi-fi, the same wi-fi connection my computer has. 

I've read a lot of help topics related to this, but I've done everything suggested and I cannot play the songs at all in Spotify on my iphone. I can play the one I downloaded from iTunes in the iTunes app, but not in Spotify. I can play all the local songs in Spotify on my computer, but not in Spotify on my phone. 

Any other suggestions? It's very frustrating as I'm about to go on a road trip and spent hours downloading songs to my computer so that I could have them on the road. 

I've included a screen dump of what it looks like on my iphone. "Master List," shown, is set to "Available offline."

[sllgatsby]

Oh, and one other detail: I am a Premium subscriber and use off-line playlists just about every day. 

[ArmsAsuncion]

Try to exclude Spotify on your firewall settings. If that doesn't work, try a different wi-fi network as the port Spotify use for local sync might be blocked by the router.