mirror lock up

Hello ! I acquired a Praktica BCA Electronic two days ago, and it worked fine I was able to take a couple of pictures Yesterday I tried to take a pic, and the shutter closed itself but didn't open again I couldn't see anything but black in the viewfinder The shutter release button is pressable...

So my beloved d700 is broken. I've never had a camera break on me. It's done less than 20k on the shutter and I picked it up one day and found no image when looking through the view finder. I've gone through all checks and YouTube vid's to see if it was a stupid fix but the mirror is just...