(1.18.2) StructureBlock for Exitportal unassigned.

[I2pRandom]

The Structure block for the Exit portal is not assigned the structure for the Exit Portal.
By chance what's the structure ID?

[yungnickyoung]

Uhh the structure block should never actually spawn into the world, so I suspect some of your other mods may be causing issues. That being said, the initial version of the tower should be called betterendisland:tower_initial