Destiny 2, like all live service titles, is prone to occasional issues, problems, and error codes. This is especially common around new content drops, the start of new seasons, or the release of new DLCs. With the release of The Witch Queen expansion, it is not surprising that this error code would start to give players problems.
Honeydew is once such error, but it will only occur under very special circumstances. According to the Bungie help page, you may have encountered this Error Code if public access to an Activity has been manually overridden by Bungie. This may occur if an issue has been found, or if an activity has been taken offline prior to a Destiny Update. Please follow @BungieHelp on Twitter for updates.”
So, the short version is that this error will occur when you are trying to load into a shared, public space in the game (Tower, HELM, etc) but the relevant server you are trying to connect to is not online.
Unfortunately, there is nothing you can do at your end to fix this issue or any of the other connection issues that Destiny 2 is experiencing right now. It is really up to Bungie to solve these consistent launch day problems.