Error while starting my project ( after running ng serve )

I had the same problem and I resolved just installing the same version of rxjs and rxjs-impat. The problem was that I had rxjs version 6.3.3 and rxjs-impat 6.4.0. I upgraded rxjs to 6.4.0 version. Having rxjs 6.4.0 and rxjs impat 6.4.0 version solved the problem

I had to downgrade rxjs-compat and was able to get past it.

"rxjs-compat": "6.3.3"