iMac doesn't work as secondary monitor with MacBook Pro 2021

Hello!

I have iMac mid 2011and MacBook Pro 2017. I connect iMac with notebook using a Thunderbolt cable and it works as a big monitor. Have never had any problem with connection.

I've just got my new MacBook Pro 2021 and tried to connect it with iMac the same as my older MacBook, but it just doesn't work.

I tried all the advices I found on the internet, but nothing helps.

The software and the cable are in order. I connect 2017 MacBook - everything works; I connect 2021 MacBook - doesn't work. Both MacBooks have the latest version of Monterey.

I also tried to downgrade the refresh rate and change the presets in Display preferences on the new MacBook - it also didn't help.

Any suggestion - what else can be done to solve this?