The tooltip doesn't load at the current time, no error shown. Also, / commands don't work.

BFA 8.3.7

Ahh, finally got the error to show:

Message: Interface\AddOns\SimpleILvl\SimpleILvl.lua:52: bad argument #2 to 'format' (string expected, got nil)
Time: Tue Sep 1 09:16:34 2020
Count: 1
Stack: Interface\AddOns\SimpleILvl\SimpleILvl.lua:52: bad argument #2 to 'format' (string expected, got nil)
[string "=[C]"]: in function format' [string "@Interface\AddOns\SimpleILvl\SimpleILvl.lua"]:52: in function <Interface\AddOns\SimpleILvl\SimpleILvl.lua:46> [string "=[C]"]: ? [string "@Interface\AddOns\CanIMogIt\Libs\AceAddon-3.0\AceAddon-3.0.lua"]:70: in function <...\AddOns\CanIMogIt\Libs\AceAddon-3.0\AceAddon-3.0.lua:65> [string "@Interface\AddOns\CanIMogIt\Libs\AceAddon-3.0\AceAddon-3.0.lua"]:498: in function InitializeAddon'
[string "@interface\AddOns\CanIMogIt\Libs\AceAddon-3.0\AceAddon-3.0.lua"]:613: in function <...\AddOns\CanIMogIt\Libs\AceAddon-3.0\AceAddon-3.0.lua:605>

Locals:

I'm not sure how that would be possible, GetAddOnMetadata("SimpleILevel", "Version") would have had to return nil which means there is something else wrong with the addon. A re-install should fix it. Let me know if this is still an issue.

Non-english client or nolib version?

I had the exact same problem and managed to fix it by uninstalling the nolib version and manually selecting the 'normal' SIL version in the Files tab on the CurseForge website. The CurseForge client didn't offer this option as far as I could see.

I also cleared my SavedVariables and did several other things like reinstalling SIL and disabling all other addons, but I don't think those steps are necessary.