Laravel Vapor - Error 500 File does not exist at path /var/task/.env.

I installed Laravel Vapor using docker. I followed all the instructions to the dot. I set 'dot-files-as-assets: true' in vapor.yml. The deployment succeeds without any error. When I open the page I see the error page with a message:

Error 500 It's not you, it's me. File does not exist at path /var/task/.env.

How to resolve this?

Thanks for any help.

Srinivas