While working on a new project in Blender 3.2.0, I ran into the following problem: I wanted to use Ctrl+J to join several meshes/objects, but it didn’t work. Blender said “Active object is not a selected mesh“. I started looking into what the problem was, and I came across the hint of not including non-mesh materials, such as lights. In the screenshot above you can see that I accidentally had a point light near my object that I selected.
That alone didn’t fix my problem though, it still gave me the same error message. As it turns out, I had an active Subdivision Surface Modifier on – the Subsurf modifier. I simply “Applied” the subsurf modifier and was able to use Ctrl+J just fine again in my Blender project!
Thank you for checking out my Blender Note! I am by all means a beginner in Blender, so I do not feel qualified to label this post as a 'tip' or 'tutorial'. However, I decided to upload this note for myself, and hopefully it can be useful to others as well.