New versions of the Labelwriter 400 (original and Turbo) do not take Generic Labels. It is an issue with the firmware Dymo have installed - it will only read the genuine labels made by Dymo. currently there appears to be no work around to solve this isses. 

The Dymo OEM labels have lines print on the back, if you use labels without these lines, the printer gives an "out of paper" error 

The only printers in the Dymo Range that will take our generic labels are the Dymo Twin Turbo and the Dymo Duo (both the more expensive from the range).

Dymo have only made this change in the last 6-8 months, old 400's will work with cheaper generic labels.