Problem with Form when using .htaccess redirect

I have two different domains directing to one page. Since I 've set the redirect, the Form does load home, but not the thankyou page.
The redirect is an if-clause. If the adress is anything other than www.example.com then set it to https:/ /www.example.com

RewriteCond %{HTTP_HOST} !=www.example.com
RewriteRule (.*) https: //www.example.com/$1 [r=301,L]

Can anyone help?

It seems it has been a Cache problem