Sprinklers eventually sink down and have grass & dirt build up under it, which prevents the sprinkler head from going down when the water shuts off.

This is what I did, it may work for you, which could save you some money by not having toto replace it or having someone break it off cause it's in the up position all the time.

You can simply use your finger or screwdriver to loosen the grass and dirt under it, and gently pull the sprinkler up to clear any dirt and other small debris which may prevent your sprinkler head from retracting.

Fix it now! Before you or someone else drives over it and you have to dig it up to replace the whole pop up & head. Plus know where your shut off valve is!!
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https://www.youtube.com/watch?v=folR7iwHagE