external monitor

I'm trying to use an old PC monitor as an external monitor - for my Macbook Air 2020.

My mac does recognize the monitor, but the monitor doesn't recognize the computer -- it keeps showing 'No signal' sign.

Here are the specs for the Built-in Display

• 13.3-inch (2560 x 1600)
• Intel Iris Graphics 1536 MB graphics

And for the Analog monitor.

• 23.5-inch
• Intel Iris Graphics 1536 MB

The monitor was made in 2019, so it can't too old, can it?

Would there be no other option but to try a different monitor? I have hooked up this computer to a TV monitor using hdmi cable, which I can't use anymore. I have used all my old macs with different PC monitors before, but this is the first time, a monitor does not recognize my mac.

Does anyone have an answer?

Thanks in advance.