Thank you again for your followup.
I believe there may be a 90 bend after duct goes into basement. I did clean out the entire run however, may be possible there me be obstruction at the 90 that wasn't completely removed. I thought that may be the cause of nor air to outside vent as well. Will do another through cleaning and follow up.
Also, were you referring to in the following statement "I would disconnect it at the floor and see if there is still good air flow". Did you mean the blower housing tube located in rear behind rear dryer panel?

Follow up;
I was able to obtain a shop vac with 7' x 2.5" hose. I disconnected the semi-rigid duct from pvc pipe going down into the floor, and then placed the shop vac hose down through the floor. I turned it on as I sent it down through the pipe. When I had finished, there were clumps of damp lint in the vacuum canister. It appears that this had clogged the 90 bend in the pvc pipe. I guess I was unable to remove all the clog with the previous methods I had tried.
I now turned the dryer on and there is air flowing through to the outside vent!
I wanted to follow up and thank you again for taking the time to assist me with this issue. I do appreciate all your assistance.