Greeting from GoVacuum,
On all Electrolux canister vacuum cleaners, there is a kill switch, that will not allow the machine to turn on without a bag in it. Sometimes when replacing the bag, the bag is placed in a position where the switch is not being activated.
When you open the bag housing, it should look like this;
You'll notice in the bottom right corner of the bag housing, the kill switch to the vacuum cleaner.
Try plugging the vacuum cleaner in, and while you are pressing this kill switch down, turn on the vacuum cleaner. Does the vacuum cleaner turn on/off when you push/release the kill switch? If it does, simply just get a new bag, and make sure that the new bag is covering the kill switch, and close the door of the vacuum cleaner.
If it still doesn't start, let me know and I'll try to help you diagnosis the machine differently. I'd say that 6 out of 10 times, this kill switch is the problem.
I hope this helps you. Please email me with any questions, or if this fix doesn't make your vacuum work. I really enjoy sharing my passion, and expertise in repairing vacuum cleaners.