Any way you can pull the grass away and take a better picture to post?

I actually found the round lid to this thing in my yard. It has NDS engraved on it. Seems like it is a pop-up emitter. I was able to just pop the lid back on to at least cover the hole, but it's still technically broken. Are these things made to be able to replace these lids (the green part) or do I have to get the whole pipe under the ground replaced? I tried to pull off the green lid/attachment, but it wouldn't budge from the underground pipe... but could just be my lack of arm strength though.

The spring strength on those things is incredible. I can pull them using my sprinkler key, but forget it otherwise unless I can get a very good grip with hands that are used to tightly gripping objects for hours at a time and holding them in finicky positions without shaking. Most people can't seem to manage.

They're made to pop when there's about 20 psi of water pressure in there or more.

The underground pipe usually connects to an offshoot pipe or offshoot connector, which leads to the base of the sprinkler/sprayer/emitter. That has a can and a body inside it.

Some brands, you can replace the body. Some you have to replace the entire can/body combo. It would be a very poor installation where the can sealed to the connector. Either the installer should use tape to install, or the plastic just won't be an issue in the first place.

You should be able to replace it with any compatible model...but the initial photo isn't good enough to tell what you have.

The majority of these, if I remember from back then, have quarter inch inlet connectors. If this is simply not popping when the system goes on, it may just need to be cleaned. Or the pipe itself could be clogged or...well, there's a lot that can go wrong here, up to the zone not opening properly at the valve.