I was just trying the new postgres 10 logical replication, and for that I had to issue a
CREATE PUBLICATION mypub FOR table mytable
on the server, and a
CREATE SUBSCRIPTION mysub CONNECTION 'host=myhost ...' PUBLICATION mypub;
The problem is that after a failed attempt (wrong host, no password, wrong password, etc) in the CREATE SUBSCRIPTION the query window does not work anymore. It's still there, but you can't run any queries on it.
You just have to copy all the text from there, close it, and launch a new one (CTR-N also doesnt work anymore in version 4, as it did in 3.x to open a new window, as CTRL-F4 or CTRL-W dont work anymore to close a window, or tab in this case, either).
Regards.