무엇을 만듭니까? means 'What you/I/we have to make?' or 'What are you making?'
-습니까 is ending for asking some finished action in past
for example, 다 했습니까?(하다(해)+었+(-습니까)) means 'It's all done?'
So if you want to use -습니까 ending for 만들다, you have to write 무엇을 만들었습니까? that means 'What did you make?'
-었- is use like -ed of korean, not same but similar
So as conclusion, -ㅂ니까? is for asking something for present, and -습니까? is ending for asking something of past, or rather it's done or not