Way to get approval status value from BP to case stage process

Hello, I'm currently trying to make a case stage process where an approval is sent out tothe selected approver by an user. I've set up so that when a case reaches the "Approval" stage a sub-process is run that will open a mini page for asking the approver name by a user.

But sub process is not automatically open that page for asking the approver name. Please see the screenshots below:

Can anyone please help with this? Any help is really appreciated!