Texture Atlas: "Not All Objects are Visible!!!'

I’ve been trying to get Texture Atlas to work, but so far it’s been an absolute nightmare. I’ve tried everything I could possibly thing of, but no matter what, when trying to use “StartManualUnwrap” under the “Auto unwrap” section in the Render panel, I’m always given the error “Not All Objects are Visible!!!”
Things I have tried in order to fix this include:

  • Making all layers visible
  • Making all objects visible, both in viewport and render, and ensuring parented objects are visible
  • Unhiding all objects
  • Deleting every object in the scene except for the group I’m trying to unwrap
  • Separating all joined objects into individual pieces
  • Joining all objects
  • Making sure even the modifiers are visible
  • Deleting and recreating the lightmap group
  • Restarting Blender, using an earlier version of Blender
  • Any and every combination of the above

I’m prtty out of ideas, and looking for any other suggestions in the meantime. I’m stumped as to what the issue could be.

I had this problem after I pressed “Finish Manual Unwrap” and then tried to start another unwrap with a new object that was not included in the initial merge. Suddenly it wouldn’t let me do it and kept pushing this error.

I’ve had significant trouble with this addon as well, whenever I’ve tried to edit geometry while unwrapping. I think it’s because the addon relies heavily on vertex groups in order to “remember” what objects were where once the unwrap is finished. It very much seems like a process of commitment, where once you decide to use the addon, you can’t make any further changes to your mesh.

I feel like there is a specific procedure to follow while using it, and I can’t seem to find any information more specific than “select your mesh, press this button, unwrap your model, and press this button”. It would be really great if someone with more experience than me with it could specifically outline all of the gotchas that can occur if certain steps are not followed, like when you realize you missed something when you were making your selections and now it’s too late to go back because it won’t let you.