I'll try to explain the best I can.
tl;dr torches on sprinklers wouldn't work one day, then worked another day
I loaded a save I've been playing and started the day with adding new sprinklers (Summer 22), went to put torches on top of the sprinklers and it wouldn't work. I already have sprinklers placed on the farm before this; some already had torches, some didn't. I tried putting torches on the older sprinklers and they worked, but putting torches on the newly placed sprinklers didn't work. I tried picking the sprinkler back up and re-placing them, tried with tile under and without, tried surrounded by crop or not, tried creating new sprinkler and lights (instead of ones I had stored); nothing worked. A few in-game days later (Summer 27), I was adding more sprinklers and this time putting lights on worked but still didn't work on Sum22 sprinklers. But, it worked after removing the sprinkler and re-placing them.
Windows 11 Home; English; Single-player; happened during both modded and unmodded