How do I ready the Cat. Conv. readiness monitor? I tried a drive cycle... on 1999 Toyota 4Runner

I looked up the drive cycle to activate or "ready" the monitor. I took it out today, and it doesn't seem to work.

I changed the O2 sensor a month ago, driven it hundreds of miles, city/highway. When I plug in my scanner, all the monitors are "ready" but just not the cat...

Asked by for the 1999 Toyota 4Runner
Possible cat problem!