Mathematica notebook autocompletion completely disappears

I had exactly the same problem today (I have Mathematica 11.2 and Windows 10): the autocomplete suddenly disappeared and neither Ctrl+K or F2 worked.

I don't have any additional packages installed; only the basic Mathematica. I tried clean-starting and that didn't work.

I managed to get autocomplete to work again by deleting the $UserBaseDirectory and restarting:

See also

• tutorial/ConfigurationFiles

• How do I fix common problems by resetting Mathematica to its default configuration?

I hope this helps!

It appears that Shortcuts` package can be involved but it is not clear how, see update in:

https://mathematica.stackexchange.com/a/85824/5478

so before you delete whole $UserBaseDirectory you can try:

Needs @ "Shortcuts`"
UninstallShortcuts[]
(*+restart*)

PacletUpdate["EntityFramework"]

should resolve the issue at this point.