Extreme Reactors Block is not connected to a reactor.

I looked this up using several different keywords, and there was absolutely nothing even close to pertaining this.

Thanks for any help.

Edit: When I click on the power tap, I apparently need 1 control rod, despite having 4.

Edit 2: After rebuilding the entire thing and getting it into working condition, I saved it and I was presented with the same error message. I don't know what the cause of it is, but it is absolutely a bug.