WoW Classic Tip: Launch your team but it launches Retail?
Fortunately, this is easy to solve!
First, make sure you have updated Inner Space. If you launch Inner Space and the Patcher window automatically pops up with any patch information, you must click the button in order to actually update. The current live build is 6497. If you are on a build older than 6463, you won't have the updated WoW detection that includes a Game Profile for Classic.
Next, make sure you have a Game Profile that will successfully launch Classic. If it's not already listed in your Inner Space right-click menu, use Add Game to add WoW Classic via its wowclassic.exe -- which would look something like this, except with wowclassic.exe instead of Wow.exe (image slightly outdated as of WoW Classic 1.13.3) ...
... you can TEST whether it successfully launches WoW Classic, by selecting the Game Profile directly from the Inner Space menu; for example, if you manually added WoW Classic, you might find a WoW Classic Default Profile. If it was automatically added, you might find one called "World of Warcraft Classic Client" for you to use. Either way, manually launch that Game Profile through the Inner Space menu and make sure it launches WoW Classic.
Next, you just need to make sure this Game Profile is assigned to your Characters in ISBoxer Toolkit
In ISBoxer Toolkit, in the top left pane under Characters, select each one that should go to classic. You will want to adjust the Game Profile assigned to the Character, to match exactly what you launched above!
This handy gif shows what to do: https://gfycat.com/PoliteQuaintHedgehog
UPDATE: As of WoW Classic 1.13.3, the file is _classic_\wowclassic.exe instead of _classic_\wow.exe