@RajithaBandara please ref this thread for solution as its same rasa --version and machine [Mac]: Rasa 3.0 error socket.io - #13 by nik202
Gotcha: You need to solve all the compatability issue or even at the time of installation or upgrading rasa 3.0.3 and incase of depedency conflict etc you can even mention this --use-deprecated=legacy-resolver.
For this current issue discussion I also recommend the following threads (highly recommend) : TypeError on Rasa 3.0 'NoneType' object is not callable - #2 by ChrisRahme | Rasa 3.0 error socket.io - #34 by nik202
If you still not able to solve this issue please do mentin me @ nik202.