FI-60 Not displaying tone on fiber

My FI-60 LFI head is not detecting my tone on the fiber. Instead of displaying the tone frequency, it just says TRAFFIC.

This can happen if the jacket of the fiber jumper is quite thick. Try a fiber with thinner jacket. The LFI head is capable of showing the tone frequency for 270Hz, 330hZ, 1Khz or 2Khz. See examples of thin versus too thick fiber in the attached picture.