It's been a while and could use some help with structure blocks. For some reason I can't get them to work. Situation:
I'm on my own created world, using Forge + OptiFine, and a bunch of mods loaded to mimic classic Tekkit (IndustrialCraft, Railcraft, Computercraft, etc etc). I want to load some buildings I created in the past, on the same version (1.12.2), so I don't have to rebuild them.
The world started as a survival world. I understood that structure blocks only work in creative mode and when in OP mode. So I'm loading my world normally, then open to lan and set to creative and allow cheats. I then give myself a structure block with the give command. So far so good.
However, I'm unable to place it. Also, I cannot get the /OP command to work. It always says "invalid command".