why won't after market ket cylinder work in my car?

Take his advice and get the OEM part for it-

Your key might be worn out. Many lock cylinders actually are made by the same manufacturer, then sold by different aftermarket companies. Unless something is coming apart in the new ones, they should keep on working unless the key is so worn that it is just barely moving the tumblers into position. It depends too by what you mean by "not working". Do you mean the key won't physically turn? Do you mean the lock cylinder turns but won't disarm an anti-theft system? If so, that's a wiring or computer problem.

The price you mentioned for new cylinders from Toyota isn't that bad, especially if the dealer can take them apart and install tumblers to let you continue using your current keys. Chrysler dealers do that all the time for their customers and Toyota is just as customer-friendly as Chrysler.

Be happy you don't have a Lexus. Two new keys cost $1500.00 and must come from Japan with a new Body Computer!

In both cases it worked fine for two weeks and then first the key would not go in and then it went in but will not turn at all as if I was trying to use the wrong key or the steering wheel was locked. Someone said I might need to replace the whole thing and not just the cylinder. But you can actually use a screwdriver to start the car fine via the ignition switch

The lock housing is bad and replacing the key cylinders is not going to work. You can try the junk yard, the lock should be at a fraction of what you need to pay for a new one.