Plugin return always blog id=1

Hi all,
i’ve a wp installation “firstwp.com” with a lot of sub-folder network “blog3, blog4, blog5”.
In normal case i see well “firstwp.com/blog5”.
With Domain Mapping plugin i want to see the blog5 with another domain “secondwp.com”.

So,
a) “secondwp.com” dns panel there is A record to “firstwp.com”
b) on plesk panel of firstwp.com i’ve set an alias domain “secondwp.com”
c) on admin panel of “firstwp.com” i’ve set that blog5 (id = 5) => “secondwp.com” primary YES.

On url “secondwp.com” always return blog1 with id=1.
Can anyone help me?
Thanks.

https://ww.wp.xz.cn/plugins/wordpress-mu-domain-mapping/