Maple Syrup is named "item.pamhc2trees.maplesyrupitem" and has been for a few YEARS now. Since at least 1.16.5.
In the lang file, the line has incorrect syntax, reading
"item.pamhc2trees.mapleitem": "Maple Syrup",
When it should read
"item.pamhc2trees.maplesyrupitem": "Maple Syrup",
It's a simple fix anyone can do in 2 minutes, I can't believe it's still here.