Your pilot is out you ahve to find where the ignition is and relight it. If you can not find it the best thing to do is try finding a professional to check the pilot light for you and fix it. if this is not the issue this could be from a gas leak.
Try flipping the circuit breaker which controls the power to the oven. This will reset the electronic controls and may cause it to work again. If this does not work, contact an appliance repair shop, do not attempt to service it yourself as working with gas appliances can be dangerous.
Your gas oven will not light, most likely your pilot light is out. I have to ask, did you forget to pay the utility bill? You should be able to light the pilot with a wooden match. Look for an access panel near the oven's base, Usually instructions are posted inside the panel. For safety check your ovens operators manual.
There are two ways to deal with this problem. One is to look into the back of the oven to see if the flame is out and use a match or a lighter to light it. The other is to call the landlord and tell them about the problem so they can fix it.