Nissan March CVT not changing gears - what shall we do?

I run a small vehicle workshop with friends and a few days ago a client brought in a recently imported (but used) Nissan March (Chassis K11-902923, Model EAEARHZK11EDA, Engine CG10(DE) 997cc, Transmission code NP-TC46NHD1AA). The car has a CVT gearbox. The car is not changing gears. It takes of smoothly but does not change gears. I am aware that one does not easily detect gear changes in a CVT car. However, in my vehicle, the car will scream and scream and will struggle to get to 80km/h. I have pushed it and it did get to 120km/h but I could tell that i was torturing the car. Occasionally, the vehicle will change a gear soon after take off, but this is rear. We took the car for electronic diagnostic testing and all systems were reported to ok.
This indicates theat the problem is most likely mechanical, rather than electronic. What could be the problem? How do we rectify it?
To complicate matters, CVT gearboxes are highly unusual here in Zimbabwe and no one repairs these boxes.

I have noticed that the oil is a very light brown. Am told that the oil should be pink. Is this true? Is all CVT oil pink?

We would like to open the gearbox and am wondering if there is anyone out there who has done this before. What should we look out for? Does anyone have a downloadable repair manual?

P.S. Importing another gearbox will cost +US$3000 from IBC Japan - this is more than the cost of importing another March.

We would greatly appreciate any help that we can get.

Regards
Lemuel Dennis
Harare, Zimbabwe
lemueldennis@gmail.com