Autocomplete in Intellisense SSMS 2017. Where'd it go? I recently got a new dev box, got my Visual Studio installed.  Got my SSMS installed.  Started writing some procs and tables... no intellisense help.
Whaaa??
All the boxes are ticked.  I'm in the right DB. I get the red squigglies if the table doesn't exist, but I have no flyout for object name completion.  Surely I messed something up because my googling tells me 2017 has much improved intellisense capabilities.
Nov 06 2018 Update
I removed my own answer saying that caching had been the culprit, because it still seems super flaky on what will and won't allow auto complete.  I can hop back to an earlier version of SMSS and get the kind of of snappy results I was used to until this version.
I've started using Azure Data Studio for day to day stuff.  It's super snappy. Lots of QoL improvements.  Not even close to enough features for server management, but lots better for general proc writing and data analysis.
Having just spent two days with the same problem, I finally found the answer (in my case).  Intellisense does not work in SQLCMD mode, and mine was on by default (Tools, Options, Query Execution, SQL Server, General, second last!)