After Sep 26th the options have been inaccessible through either the /knp chat command or the options screen found through ESC. The error thats being shown in Bugsack is the following.
This is on classic era.

4x Kui_Nameplates_Core_Config/helpers.lua:273: attempt to index field 'Low' (a nil value)
[string "@Kui_Nameplates_Core_Config/helpers.lua"]:273: in function SetMinMaxValues' [string "@Kui_Nameplates_Core_Config/helpers.lua"]:371: in function CreateSlider'
[string "@Kui_Nameplates_Core_Config/helpers.lua"]:915: in function <Kui_Nameplates_Core_Config/helpers.lua:898>
[string "@Kui_Nameplates_Core_Config/helpers.lua"]:984: in function <Kui_Nameplates_Core_Config/helpers.lua:938>
[string "@Kui_Nameplates_Core_Config/helpers.lua"]:1190: in function Initialise' [string "@Kui_Nameplates_Core_Config/create.lua"]:5: in main chunk [string "=[C]"]: ? [string "=[C]"]: ? [string "@Kui_Nameplates_Core/hook.lua"]:187: in function <Kui_Nameplates_Core/hook.lua:169> [string "@Kui_Nameplates_Core/hook.lua"]:190: in function <Kui_Nameplates_Core/hook.lua:189> [string "=[C]"]: in function Show'
[string "@Blizzard_Settings_Shared/Blizzard_SettingsPanel.lua"]:862: in function DisplayLayout' [string "@Blizzard_Settings_Shared/Blizzard_SettingsPanel.lua"]:807: in function DisplayCategory'
[string "@Blizzard_Settings_Shared/Blizzard_SettingsPanel.lua"]:749: in function <.../Blizzard_Settings_Shared/Blizzard_SettingsPanel.lua:742>
[string "=[C]"]: ?
[string "@Blizzard_SharedXMLBase/CallbackRegistry.lua"]:144: in function <...eBlizzard_SharedXMLBase/CallbackRegistry.lua:143>
[string "=[C]"]: ?
[string "@Blizzard_SharedXMLBase/CallbackRegistry.lua"]:147: in function `TriggerEvent'
[string "@Blizzard_Settings_Shared/Blizzard_CategoryList.lua"]:152: in function <...s/Blizzard_Settings_Shared/Blizzard_CategoryList.lua:150>

Locals:
self = Slider {
label = FontString {
}
display = EditBox {
}
common_name = "size"
}
min = 0
max = 100
(*temporary) = nil
(*temporary) = nil
(*temporary) = 0
(*temporary) = 100
(*temporary) = "attempt to index field 'Low' (a nil value)"

hey, having the same issue. did you manage to fix it?