OPC UA PubSub Configuration Error (PLCN0028): '...': Network address must be an url with the following pattern: opc.udp://<ip-4-address>(:port)
In the configuration of the OPC UA PubSub communication, an invalid network address is specified in the properties of a connection. This Multicast address specifies the network to which each writer contained in the particular connection publishes its data values.
Remedy
Open the properties editor of the affected connection and define a valid multicast address which also includes the opc.udp prefix and a valid port number (4840 by default).
Example