Why is my cake not rising??!

Why is my cake not rising??

Whenever I bake, my cake does not get spongy. Sometimes it gets slightly hard, sometimes it is slightly moist, but never really spongy. Here are a few details:
1. My oven: I have an old fashioned round oven, which has a glass top.
2. I was setting it at about 250 centigrade.
3. It takes really long to bake, something like 2 hrs...
4. The glass generally forms water droplets on the inside which sometimes drip into the cake.
Can you please tell me where all I am going wrong!!!
My cakes never do rise perfectly, except once when I baked it for an hour

2 days ago
i have recently got the oven checked by the manufacturer

The description of your oven confuses me. The only oven I know of that is a stand-alone, round baking oven is the one found in the eastern Mediterranean. There are likely other areas where the oven is common. These ovens can be either gas or electric. I've never seen one with a glass top, but they may exist. These ovens use the Celsius (Centigrade) scale. Your setting of "250 centigrade" is too hot for baking a cake. The correct setting should be about 175 degrees centigrade (Celsius). If the oven is operating properly there is no plausible reason for it not to properly bake a cake. So you must be doing something incorrectly.

Your comments that it takes a long time (2 hours) to bake a cake, and that water droplets form on top of the lid and drip onto the cake, hints that you may be trying to bake your cake in a covered Dutch Oven (Sometimes referred to as a French Oven). A Dutch Oven is a pot about 12 inches in diameter and about 8 inches deep. If you are using this to bake your cake you are using the wrong baking container. You should be using a cake baking pan. These pans are usually about 8-10 inches in diameter and 1 1/2 inches deep or so. There are other shapes and sizes. Cakes are generally baked in open top containers so that moisture can escape readily.

The other possibility I discern is that you maybe be using a Bead Making Machine such as the DAK which has a round baking chamber. Bread making machines do not lend themselves well to baking "breads" with a sugar content as high as the sugar content in cake batters. And they are not designed to bake a thin batter such as a cake batter. They are designed for lower moisture "doughs".

Hopefully, something in the foregoing treatise helps you solve your problem, or at least gets you on the track to solving your problem.