There can be a few things going wrong such as below:

1) You are in an HD Project setting.  Edius cannot print to tape in realtime in anything other then SD.
2) You do not have a hardware preset that matches your timeline settings.

For problem number one, there is a different process to print to an HD Deck or Camera. For Problem number 2, follow these steps.

1) Click the SETTINGS drop down and select SYSTEM SETTINGS
2) On the left side of the settings window, open HARDWARE then select Device preset.
3) On the right side, find your preset you would like to use for print to tape. Typically same preset you used for capture.
4) Click the icon and then click modify.
5) Click next for the NAME screen.
6) Click next for the Input I/O settings
7) On the output I/O settings, select Generic OHCI and the proper Video format settings.
8) Click NEXT, on the summary screen click COMPLETED.

At the timeline, press [F12] key and select your icon to begin.