Are you referring to the filter on the exhaust port, or the one under the tool caddy. If you haven't replaced the one under the tool caddy, open the cover of the caddy and look below the tools. You will be able to see the filter, and if it's dark gray or black, it needs to be replaced or removed.
Next, detach the hose and see if it will turn on without the hose. If it does, hold hand over intake to see if it shuts off. If not, a clog in the hose is likely. If it does shut off, or doesn't turn on with hose detached, it needs to be checked at the Aerus Electrolux service center near you. You could be looking at something as simple as a switch replacement, a more expensive hose replacement, or something more difficult inside the canister.
If you still have your sales agreement (pink), check the purchase date. This machine had a 25 year warranty if used with genuine bags, parts, and home use only.
If you no longer have the owner's manual, you can download one, with warranty information, from http://www.aerusvacuums.com/support/manuals/index.cfm. Go to "older models" at bottom of page, click on "down arrow", pick "Guardian (English, French and Spanish". Download to a folder you've created just for it and similar stuff for your Electrolux products. Warranty info is near the back.