It sounds like you have an oven that has a safety feature that won't allow the oven to operate without the timer being set.... You need to read the manual and follow the clock setting instructions.
Other than that I don't think anyone can give you any further guidance as you've posted very little information,,, not even the model number
The model number is usually printed on a label that's visible when the door is open, you can then google the manual,,,, other than that call your landlord