In my case, the reason was different. Try checking your heading path. For example, I had a path in the header search path:
"$ (SRCROOT) / Frameworks / CIF"
But my KIF folder was here:
"$ (SRCROOT) /../ Frameworks / CIF"
or in other words, one level down to my original root. That is why when I changed SRCROOT to the hard path, my headers were found.
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