MC 1.20.1; mod version 1.2.1-rc

When trying to make a leacher setup on a dedicated server, the leacher does not seem to do anything directly. I tested it in a singleplayer creative world and there were no issues at all.

The highlights for where the pumps should go flash repeatedly, even when pumps are placed there. The leacher's internal state (acid level, pump status) doesn't update until it is broken and replaced. Even when a valid research paper is placed (or map, for that matter) and acid is at max capacity, it does nothing. Even setting it to work on a redstone signal does nothing. Additionally, it doesn't show the red text saying "No Acid" or "No Data Source."

I have Jade installed, and it shows the correct acid level (after voiding) even when the leacher itself does not.

I have crafted three separate leachers to try this with, and none of them worked. I even did /give, and these fresh ones did not work either. I had this setup working a chunk over, but when I moved it the leacher stopped working. I even tried in other chunks in the world (and even back in that same chunk), and the same issues persist. The server logs show no errors at all.

I have recorded a short YouTube video which demonstrates these issues.

I can confirm that this is a server issue. I downloaded the world from the server and opened it in singleplayer and the leacher began working again.

Leacher from video has Redstone mode: On signal
I was unable to reproduce the issue. Anyways i still applied a possible fix to leacher and other blocks.

The actual issue was that the pumps need to be connected to the ground and not just floating in the air. The highlights go away when there is a solid block under each pump; the leacher begins working when the pumps are connected to the ground below.

Not sure if this is stared anywhere or even intentional, but good to note.

The leacher works both in the original 1.2.1-rc version and in the version with your patch applied.

In hindsight, this makes sense from a realism standpoint, but it would be nice to have it stated somewhere explicitly if this is intentional behavior.