MacBook not detecting 2011 iMac
Trying to connect my 2017 MacBook running Monterey to my 27 inch 2011 Mac to use as a monitor. I’ve got them connected via thunderbolt cable but can’t detect in Display. Any ideas?
What macOS version is the MacBook Pro running?
For target display mode, it needs macOS 10.15 Catalina or earlier.
Also, have you started Target Display Mode on the iMac (Command+F2)? It's not going to show up on the MacBook Pro, just because you connect a cable.
click here ➜ Use your iMac as a display with target display mode - Apple Support