Possible Problem #1: The dirt water tank lid may be the reason the machine is not sucking up the water. There is actually a gasket on the bottom of the lid where it connects to the actual tank itself. If the lid is not put back on properly (this is really easy to do, I've done this myself many times on my Hoover SteamVac), and the gasket is not sealing the lid to the tank, this will allow the suction to leak, greatly diminishing the suction power
to **** the water back up. Try removing the lid and reinstalling it, making sure that it's put back on the correct way, and try to see if this fixed your problem.
Possible Problem #2: The Hoover SteamVac's like yours have a very poorly thought out design flaw to them on the attachment hose. Where the attachment hose connects into the SteamVac when the machine's handle is lowered to get underneath furniture, and is close to the ground it puts a lot of stress on the hose where it connects into the machine (not the end the attachments go on, but the other end). This will cause the hose to tear at the stress point. This is a very common problem unfortunately, and I suspect might be the cause of your suction loss. To check this, remove the dirty water solution
tank from the machine completely. Step on the handle release pedal to lower the handle part to the ground. Look at the lower part of the handle portion of the machine for where the hose enters into the handle section, then follow the hose to where it connects into the machine. Right at the end of the hose, before the hose cuff that's connected to the motor, inspect this part on all sides to see if you have a tear here. If you do, this is the reason the machine is not sucking water up off of the carpeting.
Possible Problem # 3. If neither of the first two possible problems were the source of your suction loss, try this one. Turn the machine upside down (you should probably remove both the clean water tank and dirty water tank before doing this, just to ensure that no water spills when you turn the machine over) so that the brushes are facing upwards. Look right behind the brushes for two red plastic tabs that are slightly sunken into the bottom housing of the machine. Pull these two tabs upward as far as they will go. There is a metal filter screen that will be exposed when you pull the tabs. Make sure that this screen is clear of debris. This screen protects anything from going into the motor, and if it has debris blocking it, this can cause the machine to loose suction.
Also make sure that there is nothing in the clear plastic suction channel on the top of the machine where you can see the water being sucked up. Sometimes if something gets stuck in this suction chamber, this can also cause the machine to loose suction.
Also it may be that your motor is dying, and loosing suction power. Usually if this were the case the motor would continually get louder and louder, until it just stopped working. To test this, put the machine in the upright position, and remove the dirty water solution tank. If you look at where the dirty water tank rests, you should see a circular tube underneath of where the dirty water tank sits. Here's a picture that I took, that has this part circled: Put your finger down into this suction port and see if you can feel any suction coming through when the machine is running. If there is suction, then your problem is definitely going to be one of the above problems, and if there is no suction, this indicates a more serious problem with your motor. If you don't feel suction here, you may want to consider taking the machine into a repair place, or even consider to possibly getting a new machine at this point.
I really hope that this helped you find the cause of your suction loss. If you were able to diagnosis this problem, and would like me to help you fix the cause of the suction loss, I'd be more then happy to now walk you through the repair as well. Please just use the Clarification Request form here on the same page, and I will then help you out with your repair. I just ask that if this repair was helpful to you, please help other Fixya members to find it, and rate the repair helpful by clicking the 4 Thumbs Up icons in the top corner of the repair.