Are you hosting the server locally? Using a load offset won't work otherwise. If you have a dedicated server, you can set the offset in console window for that server.
Yes, I am set as the host of my server, and it's not a dedi.
I apologize for jumping to the conclusion that this mod was the source of the problem. After I saw that the loadOffset parameter was doing nothing, it was my immediate thought. I'll run Blockland vanilla and report back here if the problem seems to be stemming from the Manager.
Edit: It seems running Blockland with all default says that the loadOffset parameter just doesn't work. I set all three coordinates to zero, hit apply, and then loaded a build. I did the same thing, except set the x coordinate to a number higher than 0, and it did not load any bricks.
I repeated the same exact process using console commands, and it worked fine. I did all of this with my normal add-ons enabled and it seems the console command works fine again, although I'm sure I tested it to make sure it wasn't actually working, so it seems it may just be a problem with the manager.