I'm using 20.0.547 because it's the newest build that is supported by Redshift. I'm trying to add a simple shockwave to my scene to accompany my fracture animation but it's behaving unexpectedly. When I drop it into the scene and it generates, it works fine when it's set to the default start frame of 1, but if I change it to any other frame to put it where I need it in the animation, it stops working, even if I change the start frame back to 1. I haven't adjusted any other parameters so aside from start frame it's just a default simple shockwave sim.

Are you using the Shockwave shelf tool? If so, its emitters are animated from frame 1 or so by default. Try changing the Start Frame in the pyroburstfource_fireball node. The shockwave node uses an expression offset from this one as its start frame.