Trouble with vacuum suction

Question

I have a Thermax AF vacuum/steam cleaner. I purchased it in 1994. The problem is, when I put the recovery tank in the machine and then put the dome lid on and turn on the vacuum switch there isn't any suction. Normally if you put your hand on the hole in the center of the dome lid you can feel immediate and powerful suction. The hole in the dome lid is where the flexible hose is attached to the unit. If I take out the recovery tank and turn the machine on I can feel the suction through the hole in the bottom where the recovery tank sits. I'm not sure what the actual problem is. The recovery tank seats properly when I put it in and turn it until it drops/locks into place. The dome lid also has both rubber gasket seals so I know that isn't the problem. I did recently have to have the cord replaced. Could the repair person have done something to affect the vaccums suction? Any help would be greatly appreciated.Thanks,Kelli