Vacuum Cleaners Discussions

I am new to this forum so hello to all: I have a ~20 year old USA built HOOVER Windtunnel (Model number escapes me- I can look it up if needed). It has been very well maintained. I just replaced the power cord a month ago due to wear. I also replaced the front leveling wheels about a year ago. Recently I find it VERY difficult to push the cleaner even with the carpet adjustment on the highest setting. I can see the carpet getting sucked up against the intake area on the bottom. When the cleaner is OFF, it moves effortlessly across the carpet, and I can see a gap between the cleaner and the floor. I am using a nearly empty "Febreze" vacuum bag and have used them in the past. I took off the bottom cover, inspected the brushroll and belt both fine. I am at a loss, any suggestions would be appreciated! Thank you!