If after a sync you get a notification wiht the error 'iTunes media folder couldn't be found' it indicates that Cloud Tuner couldn't find the folder that contains all of your iTunes music. There are a number of reasons why this error might occur.
On your computer with your iTunes library ensure that your cloud service has finished syncing and all your files have been uploaded.
Under the 'advanced' tab of the iTunes preferences, check the value of 'iTunes Media folder location'. This value tells iTunes and Cloud Tuner the folder where your music is stored. Ensure that this folder exists, and is located on your cloud service. By default, this folder is called 'iTunes Media' and will typically end in 'Dropbox\iTunes\iTunes Media' when configured correctly.