How to use time stamp for high resolution screenshot from blueprint execute console command?

Hi guys,
I am trying to name the image based on a variable ‘Export Image Name’ in my example, to prevent any overwriting of images that may already exist under the same name I thought of using time stamp bool. But it seems i am doing some thing wrong.

In the above image ‘String Time Stamp’ have the information of few variable of the HighResShot.
I have set the time stamp bool to true. But the exported image have 0 byte. Can anyone please point out what am i doing wrong. Thank you every much!