The servers was currently down for MAINTENANCE.
The client was also recently updated so I recommend re- downloading the client which I linked below. If you have Windows, you can disregard as your client should update for you when you open it.
https://pokemonrevolution.net/download.php
I also honestly recommend joining the Official Discord, so you will be informed in the future when a Server Maintenance occurs in the future.
Here's a link to it also below.
https://discord.gg/98pMNxq