When an abducted news reporter’s ransom remains unpaid, her timid stalker must infiltrate a ruthless kidnapping ring before she’s executed.

This is just my opinion - that the key character is not the first person we "meet" in the logline so that sets up some confusion about who the protagonist is.

Hope that helps.

I miss some context... maybe you can specify what kind of kidnappers are they (today news reporters are kidnapped in Siria for exemple, and the movie would be different from a news reporter kidnapped in USA or Europe). And maybe you can include a clue about how the timid girl can track the kidnappers, what is her lead that the police doesn't have.

ITERATION #1: ?When an abducted news reporter's ransom remains unpaid, her timid stalker must track down the ruthless kidnappers before she's executed.

I think by simplifying the action from 'infiltrating a kidnapping ring' to 'tracking them down' makes it clearer who the protagonist is...
I've also referred to the news reporter twice with the words HER and SHE's, this might also be causing some confusion. but the main character is the stalker.