Can't connect to Minecraft Private Server - Server is online mode!? Error

Minecraft
1

Just got my family signed up for Tynker and my 1st grade is trying out the Minecraft mods. When we try to join the Tynker MC server and use /join to connect to our world, we get this error:

Exception Connecting.QuietException: Server is in online mode!

And then nothing happens… anyone have ideas? We’re on 1.16.1

2

We had an issue with the new recent server upgrades related to Minecraft 1.16.1. These should be resolved now. If you are still seeing this issue, please reach out to support@tynker.com for help.