I was monkeying around with Resharper optimization and lost Intellisense altogether! Here’s how I got it back.
In quick launch type “Statement Completion” and choose the first one “Text Editor -> All Languages -> General” to be taken to the options page for all languages.
On the general options page in the “Statement Completion” section override whatever is in the boxes “Auto list members” and “Parameter Information” and makes those checked. Such as shown here: