During your testing on pCloudy device, some times device shows blank (black) screen in between. There might be two reasons as follows
1)Device connection got broken because of Internet issue. You will see Re-connect device button is blinking in red colour at right top most corner. If it is blinking please click on the Re-connect device button to connect the device again and continue your testing. This action will bring the device in same state. You will not loose any data.
Above mentioned scenario happens because of bad internet connectivity at user's end
Please find the below screenshot for you reference
2) Device goes in sleep mode . If the reconnect button is not blinking and device screen is black, just click on Wake Up . You can use the device by clicking wake up button which will appear at top right corner
Please find the below screenshot for your reference