Welcome to Android Central! Is your web connection otherwise good? I don't have Music Manager in front of me right now, but is there a place for you to log into your Google account?
I'm having the same issue. I try to open Music Manager on my computer, but it forces me to log in for some reason, and when I do, it pops up a message saying I have no internet connection.
Newsflash: I have internet connection.
Welcome to Android Central! See what happens if you uninstall Music Manager, then reinstall it. Ideally, use a complete uninstall program like Revo Uninstaller to remove registry info as well.
I not only uninstalled Music Manager but restored my phone (HTC One M8) to factory settings then re-installed. Unable to download, requests just stay in download queue and download status icon never progresses to orange.
Had been using Music Manager for some time with no issues and recently started giving me the error. I switch the DNS from automatic to Google DNS (8.8.8.8 and 8.8.4.4) and no more issues!