Scanner reported an error Canon Pixma MG7550

I can print through my USB cable to my new Canon Pixma MG7550 on my McBook Air with OS X Yosemite 10.10.2 but when I try to scan I get a message saying

Scanner reported an error,

Cannot communicate with scanner for these reasons:

- Scanner is turned off.

- USB cable is disconnected.

Please check and try again.

I have re-downloaded the software but it still won't scan. Needless to say, it is definitely connected as it prints perfectly.

Any help gratefully received.

Processor: 1.4GHz Intel Core i5

Memory 4 GB 1600 MHz DDR3