"Unable to decode LoginPacker from null"

[IAmSyth]

"Unable to decode LoginPacker from null"

This text appears in my multicraft panel whenever someone trys to join my server. The player is left at a "locating external server" screen.
I cannot, nor can any, join my server

 

[Sleepybear]

this means your server is running the 1.12 version, but client is 1.13.
Get the 1.13 nukkit beta from https://ci.nukkitx.com/job/NukkitX/job/Nukkit/job/bedrock-1.13/