InteliSense is restricted in visual studio

This may be due to the difference in support functions of VisualStudio by language.

"We are analyzing the current project."InteliSense is restricted."""Isn't it just a temporary status display?"

In other words, "I'm analyzing," so I think "InteliSense is restricted" only during the analysis.
For example, there is an explanation of this function.
Color-coded display

The color code display uses information from the code analysis to color-coded variables, statements, and other code parts.

Hint
To disable the color code display, go to Tools > Options > Text Editor > Python > Advanced and uncheck Other Options > Color names based on on type. See Options - Miscellaneous Options

It's just that we're performing a source code analysis to achieve the color coding above and the very features that IntelliSense supports on the description page, and until that analysis is complete, IntelliSense will not be fully operational.

Regarding

If you display InteliSense items from the window menu (edit), you cannot select one shortcut item.

Is this the item that cannot be selected?
"Switch between automatic and tab-only completion of IntelliSense"T) Ctrl+Alt+Space"

It seems to be valid for C# (and VB as well?) and disabled for C++ (there are items on the menu but cannot be selected by graying out).
Python probably doesn't have that mode as well as C++.

IntelliSense

for Visual Basic code files

Auto-complementation

[Options],[Text Editor],[C#],[IntelliSense]

View name suggestions
Performs automatic complement of object names for recently selected members.

VisualStudio's IntelliSense is no longer determined by Enter (C#)

IntelliSense appears to have two modes.
It appears to be the completion mode (standard completion mode) and the proposed mode (proposed completion mode).

[CTRL] + [Space] to show IntelliSense.I think I typed CTRL+ALT+Space by mistake at this time...I didn't know IntelliSense had a mode...

I want to change the Intelligence of VSCommunity 2019 to the proposed mode, but I can't

In addition, Ctrl+Alt+Space did not respond, and the option "Edit Menu → "IntelliSense" → "Switch Mode" was similarly dimmed and unusable.

Answer
C++ does not appear to have a mode changeover.

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