I am very much use IntelliSence of VS2010. Sometimes, I can not tell when and why, the IntelliSence changes.
Example: Label lblTestTest
The normal behavoir is: I
I had same problem, but I found a fix.
In VS 2010 there is new suggestion mode, what is good, sometimes, but most of times it's not. So when autocomplete box is shown, press crtl+alt+space to go to old mode. And if you need go back to suggestion mode, press crtl+alt+space again.
In VS2017, for C++ at least, go to
Tools/Options/Text Editor/C/C++/Advanced/IntelliSense
and change
Member List Commit Aggressive
to True
Also you can use TAB instead of Enter.