Dear Ihab,
Sorry for the delayed reply.
After multiple tests, I think that the reason may be that the email action can't get the email addresses of the values you select from the Choice column as the Choice column isn't a people picker column.
You may need to add the Search for users (V2) action to get the email addresses from the choice values to generate the email action.
I don't use the Switch action in the flow. I use the Condition action in the following flow for your reference.
Best Regards,
Cliff