If the vacuum sounds like it usually does and still doesn’t pick up, you probably need to replace the belt. To check this, turn the vacuum on and lay it down sideways. Check to see if the roller is spinning. If it's spinning, turn the vacuum off. Stand it up and turn it back on. Do you hear the roller spinning. Some belts stretch over time. If the roller was spinning when the vacuum was on it’s side and stops when the roller has some pressure on it (your carpet), change the belt.
A clogged vacuum cleaner usually sounds "clogged". The noise the vacuum normally makes will seem muffled. First, Unplug Your Vacuum. Then change the vacuum bag or empty the dirt cup. If the bag is filled up more than halfway, this could reduce your suction. Throw out the bag. Look at the area that holds the dirt cup or vacuum bag. Remove any debris. Look for a filter in this area. If you find a filter make sure it's relatively clean. A clogged filter will shorten the life span of your vacuum. Make sure your filter is back in place or replaced, and reinstall the vacuum bag or dirt cup.
A lot of the current style upright vacuum cleaners have attachments and a hose on board. If you have a vacuum hose on your upright, pull it out like your going to vacuum with it. Look at the area you removed the hose from. Remove any debris. I recommend wearing gloves, and try not to use any sharp tools like a needle nose pliers that might puncture your vacuum hose.
For the final step in this vacuum cleaner repair, place the vacuum in a position where you have a birds eye view of the bottom plate. You can usually see if there is any debris that requires removal.
Here is a link that will take you to a site that shows how to access your machine to change belt or look for clogs.http://www.info-vacuum-cleaner.com/hoover-vacuum-cleaners.php
Hope this helps