iPhone and iPad not recognized under "Devices"

[user-removed]

First of all, my account is premium.

I have read the FAQs. It says if I want to sync tracks to mobile devices, I should:

1.log in to Spotify on desktop
2.connect my iPad (or iPhone) to the same wifi network as my desktop (both wirelessly)
3.log in to the Spotify app on my iPad (or iPhone)
4.import the tracks I have in my computer to "Local Files"
5.add the tracks I want to sync to a Playlist and make the Playlist available offline on both the desktop and the mobile device

6.sync the Playlist of tracks to my iPad (or iPhone) with "Devices"

It is so sad that I can do steps 1-5 but not 6—my devices are not recognized. Nothing appears under "Devices". I have seen a lot of same problems encountered by other community members here. I don't know if they have solved it, but the suggestions given are not useful to me at least. I wish a technology elite of Spotify team can help me solve this so that I can listen to tracks that I have but not included by Spotify happily ever after.

Just for your information: Right now, I have 4 tracks that Spotify doesn't include. I added them all to a Playlist. What appears on my iPad (or iPhone) is:
-1 track appears in the list but it's gray so I cannot play it; if you search this song on website Spotify, you cannot find it.
-1 track can be played but it's another version of the song that's included by Spotify, not the original version that I own. If you search this song on website Spotify, you can find it. If you click play: it plays the other version (that Spotify includes) in desktop Spotify when I don't have the version in my desktop; and it plays the version I own in my desktop Soptify when I have it in my desktop.
-The rest 2 tracks don't appear. If you search them on website Spotify, you can find them. If you click play, desktop Spotify reminds me that they are not available until I import them.
Anyway, I don't think it has anything to do with my problem.

Thank you very much in advance. I'm already desperate!!!

[Peter__ · Accepted solution]

Can you try disabling all firewalls completely on your computer and see if you can then see those devices in the desktop client?