Execution flow has a broken / missing wire

Why: An execution pin (the white triangle pins, not data pins) has no wire feeding into or out of it. UE5 can't determine when this node should run.

Fix: Click and drag from the white-triangle exec OUTPUT of one node to the white-triangle exec INPUT of the next. Every node in an execution sequence must be chained — orphan nodes are silently skipped (warnings) or crash compile (errors).