I would suggest doing a full uninstall-reinstall. That seems to be clearing up this issue for most trainers. Below are the instructions on how to do so for Mac clients:
Delete your TCGO folder, along with any downloaded installation files.
Click on 'Go' located on your top window, press the 'alt/option' key and select 'Library'.
Go to 'Cache' folder. Delete any/all Pokémon related folders you find.
From the 'Library' again, go to 'Saved Application State' and delete "unity.The Pokémon Company International.Refresher.savedState" folder.
Empty your trash and then restart your Mac.
Please ensure that you also delete all previously downloaded versions of the game. We recommend using a different web browser to download the file again (such as Firefox or Google Chrome). Visit http://pokemon.com/playtcgo
to download the latest game installer.
Pokémon TCG Online Moderator
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