The first generation iPad (with the thick, curved back)
can only run iOS 5.1.1 - In this case, the Sonos app will likely not be available in the App Store and will not be able to connect to an up-to-date Sonos system.
On June 11, 2012, it was announced that iOS 6 would not be released for the first-generation iPad, making iOS 5.1.1 the final operating system officially available for the device.
If you'd like more information on Sonos controller requirements,
check out this helpful FAQ.