I am checking the output of Caesar II (WNC case and WW+HP) against the manually calculated deadweight and weight of pipe with water of the entire pipes in the skid by means of weight report of pipes.
It is noticed that both output (via restraint summary) and my weight report do not tally.
May I know where the missing weight have gone to?

Hello...

Try running "Error Checker" in Caesar II. This will show pipe weight of the whole system. This helps me a lot in comparing the weight inspection report from heater tubes compared to CII input to have a sanity check since spring in heater tubes header is sensitive to tube weights. I'm glad I've got almost the same result with +/-1 kg difference if my memory serves me right.

No weight should go missing.
In addition to the weights shown in the center of gravity report, individual elements weights are also displayed in Pipe Properties #1 report under Miscellaneous Data in the output processor.