No referred screenshot being created and showing only blank

Hi all,
I installed a backstops tool on my machine.
-And after running `backstop reference`, it is giving me reference screenshots as expected.
-but after running the "backstop test" command to capture test screenshots it is displaying blank pages.
I am using the "puppeteer" engine.

I have given timestamp as well but still no luck.
Please help me if you have an idea about this.
Thanks in advance.