Menubar icon disappeared

Configuration Help & General Discussion
1

The menubar icon for some apps disappeared, but actually they are running in background, if I close BTT, they will appear.

But now I unchecked BTT menubar icon in the settings and applied. BTT icon is gone. Then, I restart BTT to check its menubar icon again, applied and restarted. BTT icon never come to appear.

How can I fix it?

2

you probably played with BTT's status bar item management features?
In that case you can reset everything by running the "Unhide / Show All Menu Bar Status Items" action once.