Cause
A potential definition point was placed on a connection and given a potential name and a signal name. The potential is not defined anywhere in the schematic.
Solution
Possibility 1
Enter the name of an existing potential definition for the potential definition point.
Possibility 2
Define new potential in the schematic, using, for example, a potential connection. Give this connection the name of the potential definition point for which you defined the signal name.
Refresh the connections and then start a new check run.