The ? comes on when I turn the vacuum on and it won't start

Hi you need to find a local Vacuum repair place one that deals in Electrolux, and go there and take the vacuum or the make and model, and ask for a replacement part, that is the only way that you would be able to obtain spare parts, in fact while you are there, perhaps even inquire as to how much it may cost to do it? ask for a "Quote" and go from there.

It takes the "C" (canister) bags made by Home Solutions for Aerus Electrolux vacuum cleaners.

There's a reset button on the power nozzle for the PN, but not on the vacuum.
If the vacuum won't come on, try the following:
Turn the top dial to the smallest dot. This is allows for finer than normal dust being vacuumed with appropriate bag fill. Otherwise, the pores of the bag get clogged before the bag is full. It still will, but not as much.
Using a genuine Aerus Electrolux bag (Home Solutions printed at top) also helps alleviate this.
You can also check out my tip at:

http://www.fixya.com/support/r7367127-electrolux_epic_6500_trouble_shooting

Try turning the knob on the top of the canester all the way to the right and try it again.

The bag might not be seated properly or you are using the wrong type bag.Try reseating the bag.

Sounds like the belt on the beater brush has broke.replace the belt on the beater brush.

it might be the bag or the sensor inside the machine.

Turn the knob on the top of the vacuum all the way to the right and try it again

Turn the knob on top all the way to the right

If I am right, there is a strip down the middle, on each side, they slide off then, the 2 halfs will come apart.