This only works if you are not the guild leader. If you are the guild leader and not getting guild quests, you are stuck until the devs figure out a way to fix your account.
For everyone else...
Your guild leader will need to kick you from the guild (or you can voluntarily quit) and send out a new invite. Once the 24 hour cooldown has expired, rejoin the guild. If there is a quest underway, you will not see it, but you will see the "waiting" guild quest. When the next one comes, you will be able to participate.