I have an old Insignia 19" LCD TV that I'm trying to use for a monitor for my MacBook Pro 13" 2020 MacBook

to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• on invoking Option-(Detect Display) button in Displays preferences (from another display)

so try doing some of those things and see if the display comes alive.

Yes… connections should only be made/changed/broken when both source + monitor are turned off, eg not hot- pluggable… am presuming you’re trying to connect to an HDMI monitor…,turn on screen mirroring under system prefs> Displays… hold down option while going there and you should see scaled for display, native…. Etc… should be set to either 30 or 60hz…. Cable should support hdmi 2.0 and hdcp 2.2…. Try doing a reset smc/pmu and zap pram 4x on startup…,here’s how : see link : https://www.macworld.com/article/224955/how-to-reset-a-macs-nvram-pram-and-smc.html

john b