Minecraft 21w43a cannot spawn Guardian

I want Guardian spawn as usual as
Official version

It should be spawn around monument

It didn't show up around monument

I found a monument ,but it didn't spawn Guardian
Only ancient Guardians in monument ,I tried many worlds, but the results were the same.
Have not reached spawn upper limit
I tried make it spawn ,but it didn't work

Just found a monument
Very easy , no trigger guide