Make Sure JMeter's Got HTTP/2:
You need the right things in JMeter for HTTP/2 to work, so download and put the HTTP/2 plugin in JMeter, okay?
Put HTTP/2 in Your Test Plan:
Go to "Test Plan" -> "HTTP Request Defaults."
In the "Advanced" tab, check the "HTTP/2" option.
This will make all subsequent HTTP Request samplers use the HTTP/2 protocol.
Make sure the browser you're using does HTTP/2,
And make it use JMeter as its proxy, somehow.
Do the HTTPS Thing in JMeter:
Because HTTP/2 is often over HTTPS, make JMeter do HTTPS too,
You'll find it in "HTTP(S) Test Script Recorder," and the "HTTPS" tab, hit "Import from JMeter" and do what it says with the certificate thing in your browser.
Manual Recording Maybe?:
If it's not doing what you want, just make the HTTP/2 requests yourself, like,
Look at the network stuff in the browser tools and put what you need in JMeter.
If it's Not Working, Look at Logs and Stuff:
Check JMeter's log things, might tell you what's going wrong.
How to check log :
In jmeter UI Interface:
When you're running JMeter with the GUI, you can see logs at the bottom part of the window, in the "Log Viewer" panel.
go to "Options" -> "Log Viewer" to turn it on.
JMeter also keeps a log file named "jmeter.log."
You'll find this file in the directory where JMeter is installed, or in the "bin" folder.
Just open that file with a text editor or something, and you can see all the logs and stuff there.