Pretty long errorcode

4x SavedInstances\SavedInstances-@[email protected]:4193: attempt to concatenate local 'kabbrev' (a nil value)
SavedInstances\SavedInstances-@[email protected]:4193: in function ShowTooltip' SavedInstances\SavedInstances-@[email protected]:2679: in function OnEnter'
ElvUI\Modules\datatexts\datatexts.lua:66: in function `onEnter'
ElvUI\Modules\datatexts\datatexts.lua:229: in function <ElvUI\Modules\datatexts\datatexts.lua:227>

Locals:
self =

{
SetDefaultModuleLibraries = defined @ElvUI\Libraries\AceAddon-3.0\AceAddon-3.0.lua:398
localarr#categoryrow = {
}
EnableModule = defined @ElvUI\Libraries\AceAddon-3.0\AceAddon-3.0.lua:363
modules = {
}
CancelTimer = defined @ElvUI\Libraries\AceTimer-3.0\AceTimer-3.0.lua:145
RequestLockInfo = defined @SavedInstances\SavedInstances.lua:2783
localarr#blankrow = {
}
TRADE_SKILL_LIST_UPDATE = defined @SavedInstances\SavedInstances.lua:4890
SetDefaultModulePrototype = defined @ElvUI\Libraries\AceAddon-3.0\AceAddon-3.0.lua:440
defaultModuleState = true
IsEnabled = defined @ElvUI\Libraries\AceAddon-3.0\AceAddon-3.0.lua:482
localarr#columns = {
}
ScheduleTimer = defined @ElvUI\Libraries\AceTimer-3.0\AceTimer-3.0.lua:92
DisableModule = defined @ElvUI\Libraries\AceAddon-3.0\AceAddon-3.0.lua:381
ADDON_LOADED = defined @SavedInstances\SavedInstances.lua:2763
RegisterMessage = defined @ElvUI\Libraries\CallbackHandler-1.0\CallbackHandler-1.0.lua:116
UnregisterMessage = defined @ElvUI\Libraries\CallbackHandler-1.0\CallbackHandler-1.0.lua:179
RegisterBucketEvent = defined @HandyNotes_DraenorTreasures\libs\AceBucket-3.0\AceBucket-3.0.lua:213
memcheck = defined @SavedInstances\SavedInstances.lua:3266
scan_item_cds = defined @SavedInstances\SavedInstances.lua:4784
localarr#showcol = {
}
SetEnabledState = defined @ElvUI\Libraries\AceAddon-3.0\AceAddon-3.0.lua:455
enabledState = true
RegisterEvent = defined @ElvUI\Libraries\CallbackHandler-1.0\CallbackHandler-1.0.lua:116
localarr#RefreshTemp = {
}
IterateModules = defined @ElvUI\Libraries\AceAddon-3.0\AceAddon-3.0.lua:468
TradeSkillRescan = defined @SavedInstances\SavedInstances.lua:4869
CHAT_MSG_MONSTER_YELL = defined @SavedInstances\SavedInstances.lua:2990
localarr#wbsave = {
}
OnInitialize = defined @SavedInstances\SavedInstances.lua:2607
NewModule = defined @ElvUI\Libraries\AceAddon-3.0\AceAddon-3.0.lua:266
GetModule = defined @ElvUI\Libraries\AceAddon-3.0\AceAddon-3.0.lua:241
ShowTooltip = defined @SavedInstances\SavedInstances.lua:3724
defaultModuleLibraries = {
}
TimeLeft = defined @ElvUI\Libraries\AceTimer-3.0\AceTimer-3.0.lua:170
localarr#holidayinst = {
}
localarr#instancerow = {
}
RefreshMythicKeyInfo = defined @SavedInstances\SavedInstances.lua:2846
ScheduleRepeatingTimer = defined @ElvUI\Libraries\AceTimer-3.0\AceTimer-3.0.lua:127
CancelAllTimers = defined @ElvUI\Libraries\AceTimer-3.0\AceTimer-3.0.lua:158
toonInit = defined @SavedInstances\SavedInstances.lua:2592
localarr#lfrbox = {
}
GetName = defined @ElvUI\Libraries\AceAddon-3.0\AceAddon-3.0.lua:310
SetDefaultModuleState = defined @ElvUI\Libraries\AceAddon-3.0\AceAddon-3.0.lua:418
localarr#instancesaved = {
}
localarr#categoryshown = {
}
RefreshDailyWorldQuestInfo = defined @SavedInstances\SavedInstances.lua:2924
scale = 1
RegisterBucketMessage = defined @HandyNotes_DraenorTreasures\libs\AceBucket-3.0\AceBucket-3.0.lua:229
orderedModules = {
}
baseName = "SavedInstances"
Disable = defined @ElvUI\Libr

You grabbed something wrong.

Make sure you download the files from the code tab then copy the contents within the included Saved Instances folder ONLY.

did you try deleting your addon saved variables? Might be the addon is choking on an unexpected value

kabbrev is loaded with a value from
for toon, t in cpairs(vars.db.Toons, true) do
...
local kabbrev = KeystonetoAbbrev[t.MythicKey.name]

the last line i copied is the one reported for the crash

I didn't say that ;p
The code is using a variable with that name though and it gets filled with values from your saved variables (as far as I understand the code).
That however is causing the error.

So my guess is that your saved variables don't contain some values the code is expecting (and lacking error handling in case they don't exist). That causes a nil error.

By deleting the settings for SavedInstances you can force it into default settings which might resolve your issue.
Do a backup of your WTF folder to easily restore them later in case it doesn't help