Which software were you running?
Retail latest version as of this posting.

Have you read the changelog?
Yeah

Please describe the bug.
Get this error when using that addon. Just logging in has this error.

Bagnon_ItemInfo/Defaults.lua:179: attempt to call global 'IsAddOnLoaded' (a nil value)
[string "@Bagnon_ItemInfo/Defaults.lua"]:179: in function <Bagnon_ItemInfo/Defaults.lua:174>
[string "@Bagnon_ItemInfo/Defaults.lua"]:225: in function <Bagnon_ItemInfo/Defaults.lua:220>

Locals:
(*temporary) = nil
(*temporary) = "Bagnon_Config"
(*temporary) = "attempt to call global 'IsAddOnLoaded' (a nil value)"
AceConfigRegistry =

{
validated = {
}
tables = {
}
callbacks = {
}
}
optionDB = {
args = {
}
type = "group"
}
AceConfigDialog = {
tooltip = AceConfigDialogTooltip {
}
BlizOptions = {
}
popup = Frame {
}
OpenFrames = {
}
Status = {
}
frame = Frame {
}
}
Addon = "Bagnon_ItemInfo"

Please describe how to reproduce it.
Log in to the game.

Any Screenshots?
If applicable, please add screenshots to help explain your problem.

Error Logs are Important!
Type /console scriptErrors 1 in the chat and reload the game. If an error window appears when reproducing the bug, please write here the first message (labelled 1/Many) that appeared. ⚠️ By default, the last error message is shown, not the first! You need to navigate back to the first error.