I am trying to paste a group of objects into a text chain to anchor it so it will flow with the text. A single object works fine. But the paste option is dimmed if I try to paste two (or three) objects that I have grouped together. The group is a simple object frame with a graphic with a text frame on top. The paste option is dimmed even for a frame with no graphic grouped with a text frame on top.
Something must be wrong in your setup.
I've just tried this, created a new doc, filled a text box with some placeholder text, made a group of squares and one text frame, grouped and pasted into the main frame with no trouble.
Something could be wrong with your object styles - check if any objects styles are applied to anything. Maybe a grep style applied to anything ? You kind of need to debug this, since we don't have access to the file.
Ultimately, create a new document and just rebuild a random text box with a random group of objects. If this works, then your initial file must have something in it that prevents copy pasting.