The nascent operating system seems to be the sticking point for operators, whose job it is to flog as many phones as possible. "If the Lumia with the same hardware came with Android in it and not Windows, it would be much easier to sell."
Another unnamed network spokesman said, "It's good for operators if we can reduce the dominance of Apple," but with iOS or Android owners understandably reluctant to abandon their stockpile of previously purchased apps, I can see how convincing people to switch is an uphill struggle.
Networks are reportedly frustrated with how little cash Microsoft is spending on marketing Lumia devices. If true, that's dismaying news. With Apple to beat, Microsoft will need to plough a tonne of cash into making people aware of Windows Phone's existence.
Personally I'm a fan of Windows Phone, and I think Nokia's Lumia devices are the best phones running that operating system by a country mile. I'd like to see them do well, but how to make them more popular?
Smart phone analyst Ian Fogg tweeted an excellent point, that the Lumia's weakness in Europe means dominating the US is key to boosting the Windows Phone operating system. Otherwise apps for the platform will dry up, and Lumia phones will end up devoid of tempting software.
The Nokia Lumia 900 has just launched in the US, so I'll be watching, hawk-like, to see how it fares.
Are you a Lumia fan? What could Microsoft do to make Nokia phones look more appealing? Let me know in the comments or on our Facebook wall.