WowAce

I'm playing WoW Classic Era version 1.15.4.56857. Version of the addon I'm using is: HandyNotes-v1.6.21 and in Curseforge it's showing Game Version 1.15.3

When launching the game (or reloading UI), I get this LUA error: 

15x HandyNotes/HandyNotes_EditFrame.lua:205: CreateFrame(): Couldn't find inherited node "OptionsButtonTemplate"
[string "=[C]"]: in function `CreateFrame'
[string "@HandyNotes/HandyNotes_EditFrame.lua"]:205: in main chunk

Locals:
(*temporary) = "Button"
(*temporary) = nil
(*temporary) = HNEditFrame {
BottomLeftCorner = Texture {
}
titleinputbox = EditBox {
}
descframe = Frame {
}
descscrollframe = HandyNotes_EditScrollFrame {
}
TopLeftCorner = Texture {
}
RightEdge = Texture {
}
desctext = FontString {
}
continentcheckbox = CheckButton {
}
backdropInfo = <table> {
}
TopRightCorner = Texture {
}
icondropdown = HandyNotes_IconDropDown {
}
descinputbox = EditBox {
}
titleinputframe = Frame {
}
BottomEdge = Texture {
}
title = FontString {
}
TopEdge = Texture {
}
titleTexture = Texture {
}
titletext = FontString {
}
Center = Texture {
}
CloseButton = Button {
}
LeftEdge = Texture {
}
BottomRightCorner = Texture {
}
}
(*temporary) = "OptionsButtonTemplate"

Please advise. Thank you