Got this message. I'm just following directions

How did this happen?

I have no idea, but it won't let me place a pipe block in its place. You can actually get the breaking animation of that invisible block but it immediately reappears. I'm playing on AQM2, it happened when I upgraded from mod v 1.5.2a to 1.6.

To remove it, you can enable debug commands on the server in the modern_industrialization.toml config file, and then run /mi pipes clear <x> <y> <z> if my memory is correct.