The new launcher defaults on using the most current version of Minecraft that has been released by Mojang. Unfortunately, servers like Blocklandia aren’t able to immediately update to the new version (we have to wait for plugins to update first.) When the server is not the same version as your Minecraft client you’ll see an “outdated server” message when you try to connect. This means you need to switch to the same version that the server is on, in order to join us.
The good news is, with the current launcher, it’s extremely easy to switch between versions. The first step is to click on the Edit Profile button in the bottom left side of the launcher:
Then change the version your profile is using to the previous version (or the version of the server) by clicking on the arrow after the Use Version: box.
The server is currently on release 1.16.3
I like to set up a profile for each version (labeled with the version number) so that I can easily switch back and forth as needed.