I've come across this problem with this iterator before. It does not seem to pass on the knowledge of the type of file it is producing (What you have named as File).
This means when you attempt to connect the iterator output to your Make NetCDF Raster Layer tool the tool is unable to pick up on the file schema and will not allow you to choose the fields you need to choose (variable/X/Y/ Band etc..).
The solution is to temporarily point the tool to a source dataset as shown below, so not the iterator output, complete the rest of the tool and OK it. Your tool will now be connected to the source data, simply connect the iterator output to the tool and delete the temporary source input.
By connecting it to the source data you have been able to complete all the parameters, break the link to the source data does not clear these parameters so these pre-filled parameters mean the tool will now connect to downstream tools and colour up correctly.