I can explain it. The Lagoon is a new area, only introduced with some of the new updates in Nov 2021, which was the open beta for testing the new content. Since then the Development Team had some personal emergencies, and I think there was some turnover by the end of it, so not all of the bugs associated with the Lagoon (or Fogstone Mines accessible from the Lagoon) have been fully worked out.
The first quest to gain access is "Trouble Afoot". The entrance appears right in front of Baron Sizzlepot in Smuggler's Cove. That should be when you get permanent access to the Lagoon. However, when you complete the quest (which just includes walking all around the Lagoon), you lose access to the Lagoon, and the entrance in Smuggler's Cove literally goes away. The second quest, which you can't get until "Trouble Afoot" is complete, is "Eliminate the Fog", which I think they deactivated so people won't get stuck, but that didn't give access to the Lagoon again.
If your glitch is that you still have "Trouble Afoot" active and also cannot access the Lagoon, that is a new one to me. However, so many people have problems that once they start fixing the Lagoon access problems, yours should be fixed along with everyone else's. Until then, it's a known stuck quest. Know that you are not alone, and we're all waiting slightly impatiently together!