Just for fun, since support won't be open until at least Monday - Go to 2020 and add a new client, using an existing client number and see what happens. 

Try the icon just to the left of ef - The tumbling blocks - that refreshes your client list.

In 2020 - is the same thing happening for all modules? 

In 2020 - Are you sure that you did not click one of the filters on the left? (Click All Clients)

Merry Christmas and a Bah Humbug!