Working with Mathematica 11.1.1.0 - code assist does not work at all. All the Options Inspector fields seem correct. Could be some missing files from $BaseDirectory? That directory does contain a file "CodeAssistHistory9.0.m" does seems odd.
Mathematica 6 and 9 were both loaded on this machine. Could it be that the installation failed to copy some files as a result.
I could try a reinstall but the first install had problems that Wolfram support took about 10 days to resolve.
$UserBaseDirectory. A colleague of mine has the same problem. Maybe some paclet Wolfram pushed in the last few days? – Sjoerd Smit Nov 23 '17 at 14:20