What behaviour is observed:

Did not change the skin on command

Steps/models to reproduce:

Update to latest protocolib
and run the /setskin command on a player

Plugin list:

protocollib 4.6.0-snapshot-b476

Environment description

Bungeecord and paper 1.16.1

Plugin version:

changeskin 3.1 snapshot-0d7ee09

Error Log:

https://paste.gg/p/anonymous/cf515e565b4c4226804985431d054515/files/290c0f4b53d047e2b3d8a05be5c14897/raw

For me it works using the specified Paper version. Do you have a plugin installed, which provides support for the 1.16.2 protocol?

Same exact error here, using:
Paper version git-Paper-144
ProtocolLib version 4.6.0-SNAPSHOT-b478
ChangeSkin version 3.1-SNAPSHOT-0d7ee09

I guess the best thing to do is just rollback protocollib to a previous version for 1.16.1, this works fine on 1.16.2