Braccio ++ Board Power Issue

Hi,
as part of a project with my university i have been given an Arduin Braccio ++ robot to carry out part of the project. the robot is connected to an Arduino Carrier Board and having started today have already a ,major issue. as soon as i plug in the board power supply and connect to my PC via USB the board scrren is still asking to ''Please Connect Power.'' is this possibly a hardware issue?

Yes

To which board are you connecting the power supply, Braccio Shield or Arduino?
Measure the voltage produced by the power supply.

Be descriptive.

I plugged it into the arduino board. I’ve also tried another board on another braccio ++ and am having the same response so I assume it’s a power issue but am using the cable and transformer that came with the robots

Measure the volts output of the power supply.

The documentation shows using the power jack on the Braccio.

I measure the voltage and its 5V at the output, it says on the board it should be 7.4V input so this leads me to believe its an issue with the power supply.

What says what should be?