Keyboard Command Tab doesn't work sometimes

I have Macbook pro, I use Command Tab to switch between tabs and sometimes when I do that it won’t work like I can’t switch from one tab to another. Is it a major problem or does it happen to anyone.
Thank you

I am confused. When I use COMMAND+TAB I cycle through open Applications. Did you remap your keyboard shortcuts or are you referring to a different keyboard shortcut?

Just for the record:
There is a Mac standard shortcut to navigate through window tabs: ⇧⌘[ (right to left) and ⇧⌘] (left to right).

This happens on my desktop on Sierra. But it only started happening recently. If I hit it a 2nd time then it works.