How to make site A.com totally 301 redirect to B.com

Hi all, I meet one issue recently and do not know why.
A.com 301 redirect to http://www.B.com - site A has http://a.com and https://a.com, site B only has http://, no https://
I enter http://a.com or http://www.a.com on google browser. it will redirect to http://www.B.com, but https://a.com has no reaction.
Anyone know how to solve it?

clarkma said:

site A has http://a.com and https://a.com

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First, try to make sure these redirect to same version. You can redirect https version to http

and then completely redirect http://a.com to http://b.com

Remember to use wildcard redirect. if you're using cpanel it already have redirect section with wildcard option