Zlata

Hello, I need help. I have Canon5D Mark iii and external flash Sunpack RD2000. In a store it was working, but when I came home I had to adjust the camera to my needs, but I can't activate the flash. It says that the flash is either incompatible or flash's power is turned off. I took a look at some videos on youtube, but I still can't fix it. Can somebody explain to me please what do to in settings? Thank you 🙂