Hello, I am afraid your engineer could be wrong. Yes it is a sealed system so there is a very small probability that there could be a blockade in the line. It could come from scales developing inside the pipes in time and could clog the small capillary tube. But if it is a blockade, still it can be repaired and the compressor should start even though if there is a blockade in the system. What I think is happening to your compressor is that it can not start. Either you have a faulty starting component or you have a defective compressor.
You can try replacing the starting component since it is a DIY, but after replacing this starting component and still the compressor can not start, then I am afraid you have a defective compressor which would need replacing and id no longer a DIY.
The starting components consist of item 733, 734 and 735 in this parts diagram. Please click the blue word. Un plug the unit first before doing the repair.