Cake don't rise

[BengalLioness]

Okay so I have always baked the same old cake with the same old ingredients for the last 6 years.

Suddenly last month my cakes no longer rise and are so dense it's just doing my head in. I thought I was doing something wrong with the cake first but now I see my puff pastry won't puff up either !

I have a fan assisted oven.

How can I fix this? Do I need a completely new oven or something particular I need to sort out. Stressing me out.

Can you get an oven thermometer to double check that its actually heating up to the temperature indicated on the dial.
Are you using something like baking powder or bicarbonate - it might be worth trying a brand new tub - the raising ability degrades after they've been open for a while.