*ngIf is not working

Make sure that you have spelling right i.e. ngIf not ngif or ngIF etc.

Unfortunately for me, the issue was that I forgot to import the BrowserModule or CommonModule. I'm working with Angular 9 and spent over 30 minutes looking for what wasn't lost.

Try this way -

*ngIf="!auth.isLoggedIn == true"

I know it is weird , but it worked for me