Please check the following in-game:
- Press “Esc” on your keyboard and select “Settings”, under “Interface” select “Names” to make sure you have “Show Your Name” selected.
- Verify that you're still in a guild. Press “G” to bring up your guild window; if you are unable to bring up that window then you are no longer in a guild.
If you have “Show Your Name” selected and you are still currently in a guild, ask an officer of the guild to remove and re-add you to resolve the issue.