Join key without both columns

A key pair on a Join node names a column on one side only. A join compares the two columns of each pair, so a pair with one column cannot be compared, and the workflow cannot run until the pair is complete.

What to do

Open the Join node's settings and choose the column on both sides of the pair, or remove the pair.

Where it comes from

Shown by Join. It is one of the messages about a node.