Visit Length

I keep getting 1 sec visitor lengths for a Word Press-based web site. I have statcounter installed as a WP Plugin and have the options set for footer and forced invisibility. Any idea why I cannot get this metric to work?
I see the following text in the Visit Length Statistics Page:

"If you only install the StatCounter code on one page of your website and your visitors never reload that one page. Then your visit length will always be less than 5 seconds! It is highly recommended to install the same code on all pages of your website you want to track."

I would not expect this to apply to WP-based websites. What am I missing?

Many Thanks