Postgresql Transaction ID Not Found
I assume you found a solution, but for anyone else that finds this post, I had the same issue and I just closed PG Admin 4 and restarted it and it cleared up.
To anyone who has this problem, all you have to do is:
1) Reconnect to the database
2) Open a new Query Tab. (Run your query here)
You're welcome.
For me helped changing 'localhost' in connection settings to '127.0.0.1', as mentioned here: https://stackoverflow.com/a/59747781/2590805