Xbox 360 Achievement "Synthesis Skill 100" Not Unlocking

Platform: Xbox 360
ISP: Comcast
Type of Internet Connection: Cable
Internet Connection Speed: 120Mbps
Date & Time: 11/22/2015
Frequency: Always
Character Name: Gryffen
Race: Hume
World: Valefor
Main Job: Bard
Support Job: White Mage
Area and Coordinates: Port Jeuno <J-8>
Party or Solo: Solo
NPC Name: Zuah Lepahnyu (or any Traveling Bard)

Steps:
1. I have 102 Goldsmithing skill; the achievement is for reaching synthesis skill 100.

2. I clicked the Traveling Bard NPC to unlock the achievement.

3. Traveling Bard NPC does not show the achievement in the list to be unlocked; NPC says, "You have no achievements to unlock." Every other achievement has been unlocked except for this one - "Synthesis Skill 100".

4. I tried other Traveling Bard NPCs; none of them seem to recognize achievement unlock-ability for a skill level over 100.

5. Others have reported they have experienced the same issue.

6. I also play on PC, which is where I leveled the synthesis skill to 100 and beyond. As Xbox 360 access for FFXI is being shut down in just a few months, I wanted to unlock my final achievements for the game - before I am no longer able to.