I was preparing a beacon on the nether. Once I built the tower I took the coordinates of the beacon from the Targeted Block section of the F3 screen and go to the nether roof to build a hole in the ceiling until I reach bedrock.

But I noticed it didn't power on, that's when I sit on top of it and turns out both X and Z coordinates are off by 1.

In the screenshot you can see me sitting on top of the beacon (where X and Z should be the same as the beacon).

PS: I selected MC version 1.17.1 in this summary because it would not let me choose the right version but you can see i'm playing on version 1.16.5.

Edit: returning to the overworld fixed it.