I’ve forwarded my email-id to another email-id but I am unable to receive emails on the 2nd email-id, why?

Please check that you have entered correct spelling for your 2nd email-id. If you are sure that you have then try sending a test message to the 2nd email-id and see if you receive it. If this doesn’t work for you, then remove the forwarding and check whether you can receive emails on your email address or not.