When using a back on this camera a 2-shoot error always occur... Below is a trick for to avoid the 2-shoot error.
1. On the Hasselblad V series the small PIN - image below - are often grey or almost black. The digital back needs a PIN that is has a pure reflective silver/metal color to receive the wake-up signal. This can be done by cleaning the PIN or make a line with a silver-pencil. This will re-establish reflection and the back will work in 1-shot mode.
2. Use the wake-up cable from Phase One. Press wake-up cable, to wake up the back. Next step is to press the exposure button to start the exposure. Or the use of the Kapture Group One Shot cable.
Image of the PIN that needs to be clean and reflective: