When I first joined the Immortal Flames, I started doing my supply/provisioning missions (this was probably within the 1st or 2nd week after launch). Then, I noticed that I had no GSM supply mission but I figured that it was just the way the game was designed. Upon speaking with one of my friends today, I found out that she has been able to do missions for GSM since she joined her GC. When I asked someone in-game to confirm, they advised me that the GSM missions are available to them as well. I also saw a post somewhere on this website where someone reported this same bug but I was unable to reply to the same thread since I just created a profile a few minutes ago (so I hope I am not posting this in the wrong location).

Time: All times
Frequency: All times
World name: Gilgamesh (NA, non-Legacy)
Character name: Zack Strife
NPC name: n/a
Monster name: n/a
Class/Level: All
Party or solo: n/a
In-game time: All
Area and coordinates: n/a
Steps:
1. GSM supply mission is not available for me to complete
2. It is not listed in my Duty > Timers menu or the Grand Company's supply/provisioning missions turn-in list