@k4r4koyun said:
BTW which version of Wireshark did you guys use? I have 2.4.5 on my box and I believe there might be a bug with the challenge on that version
The challenge is bugged. Do not try to do this one with up-to-date Wireshark installed in Kali Linux. I have downloaded Wireshark 2.1.1 from their site on my Windows computer and the flag is there.