RE: cooler refrigerant

Shake is necessary as the refrigirant is a mixture of R-134a and lubricant for compressor. If you do not shake, the compressor may run dry and wear prematurely.
On the not working topic, you should measure the pressure before adding. That way, it will help you to see what wasthe problem: it could be leak problem, clutch problem, blockage, air trapped, or just fuse or relay problem.