I have some problems with faces and couldn’t picture them at one point. After a lot of practice I can now picture them without problem (though I still don’t always recognize people that I know if I haven’t seen them in a few months). I wrote about a couple of the exercises I did here.
It might be worth experimenting with something like this: stare at an object and then close your eyes and see if you can hold it in your mind, even for a moment. It might not work right away, but I’d keep practicing. Try to mentally trace the outlines of the shapes and get a sense of the 3D shape and its position in the relation to you. It might take a long time (even a couple of years), but something like that has worked for me.
There is also some great advice here.