SQL statement field of Execute Select SQL operation is grayed out

Question

I'm using Execute Select SQL operation, but the [SQL statement] field is grayed out and cannot enter anything in the field.
What is the cause and is there any workaround for this?

Answer

Execute Select SQL operation checks the establishment of communication with the connection destination when opening the operation's property and grays out some property items if the communication is not established for some reason.

1. Close and reopen Designer
2. Check the connection settings and the establishment of communication with a connection test