Need to pass emissions! new cat!!?

Replacing the cat was probably completely unnecessary. That said, there is a SIMPLE way to find out if the monitor for the cat is 'ready'. Go to ANY auto parts shop and have them connect a code reader. If the monitor ins't ready, that will show up on the scan.

Do a web search for "drive cycle" for your type of car. If you follow this to the letter the cat monitor can be set in less than 20 minutes of driving. Be aware that all manufacturers that I'm aware of require you start this procedure with a cold engine. In other words, the engine coolant sensor must have the same reading as the air intake temp. sensor so let the car sit over night.

You don't have to replace a catalytic converter if the monitor test was not complete yet. The catalyst monitor won't set for a number of reasons if it hasn't run and been completed. For starters you need a gas tank that is 3/4ths full.

it is not so much that the cat is not ready but the self tests have not run to conclusuion yet. look up the drve trace pattern for your vehiocle and math that for 3 days and try again. it should be that simple. if the cat is new, that can effect the tests on the car also.

You're going to have to go through a drive cycle without the car throwing any codes. The drive cycle will change from each manufacturer. Check the owner manual, it will tell you exactly how far you need to drive. Just because the check engine light is off, does not mean the codes are cleared and you will pass. You still have to drive for x amount of miles without any fault in the system.

It has to go through a "drive cycle" which is different for each manufacturer. It is possible to drive for months without the cat monitor ever becoming ready. Without knowing what sort of car, truck, or moon rover it is I can't help you.

What kind if it's Egyptian cat there's no need for it

If there is no check engine light. it is ready.

the converter was "ready" the moment is was replaced.............you will need to have the vehicle retested and findd the results