Hi stornell,
To resolve this error, please follow these steps:
1. Please remove the paper cassette and ink cassette from your SELPHY CP900.
2. Manually remove any paper that may remain inside of your printer.
3. Make sure that there is paper in the cassette. Also, please make sure that the paper you are using is for the SELPHY CP900 and not regular inkjet paper.
4. Reinsert both cassettes into your SELPHY CP900.
5. Attempt to print.
If the error returns, please contact our support group using the following link:
https://www.usa.canon.com/internet/portal/us/home/contactus
