Photovoltaic inverter open circuit

An open circuit fault, reflected as maximum cell's output voltage, with no ability of current to flow (hence no power output) is often caused by broken cells, damaged connections between them, loos. [pdf]
[FAQS about Photovoltaic inverter open circuit]

Measure the open circuit voltage of the photovoltaic panel

Read the voltage on your multimeter and compare it to the open circuit voltage (Voc) listed on the back of your panel. If your voltage reading is negative, reverse the probes and measure again. [pdf]