Vizio TV (VA26LHDTV10T mfg. 2009) shows "No Support!" Roku Express 3930 is connected to HDMI1, and TV is set correctly to Source HDMI1. Same problem if using HDMI2. Does Roku Express 3930 not support this Vizio TV?
Try a different HDMI cable and make sure you're using the supplied power adapter and not the TV's USB port.
I agree with renojim. It could be the USB power that is giving you problems.
I'm guessing that "no support" message is from your tv, telling you that the Roku is sending a signal in a resolution which the tv does not support. If that's the case, you should see the normal "bouncing letters" Roku startup screen, but lose your picture when it tries to load the home screen.
I'd suggest trying the Roku on a different TV if one is available, especially if it has a working Roku. If it comes up okay there, go into Settings > Display type and change the Roku to the actual resolution of the problem set instead of the "auto" setting. When you get to the countdown screen click on the "yes" option. Now move the Roku back to the first set and see if it works.