It still has a leak that they haven't detected yet. The system should still have dye in it. The dye fluoresces or lights up with Ultra Violet light. You can buy a UV light on Ebay for less than ten bucks. Make certain that you get protective glasses because the UV light can damage your eyes.
You should be able to see the leak by following all of the AC components with the light. The dye will look like radioactive snot. It will be easy to see with the UV light.
The first place I would look is the AC drain on the right underside of the car right below where the passenger's feet would be. This drain takes the condensation away from the evaporator core, which is inside the car behind the glove box. You won't see the actual leak but you will see the results of the leak coming out of the AC drain.
Most techs forget to look here. I expect they looked at all the easy places but forgot this one. If it's leaking there, it's an expensive repair. I think one of these shops owes you because you paid to have the system diagosed and they didn't do a thorough job.
Thank you in advance for accepting my answer. If you feel that my response isn't helpful, please let me know and I will release your question back into the list.
I don't think any of the shops have actually found the main leak leak. They might have found a very minor leak or maybe no leak at all but they still replaced a part.
If they add freon and it works for a while it still has a leak.
I'm sorry that you feel that my answer isn't helpful. I will release your question.
The last repair at the Nissan dealership, low freon by 0.3 lbs and subsequent problem happening immediately indicates fault might be electrical.
When the AC fails, check if the compressor and condenser cooling fans are working. It could be due to a faulty relay, failing compressor clutch or electrical controls and testing would have to be carried out when the problem happens.