Pro-site plugin multi language problem

I am using Pro sites plugin in my site. My site is dual language site. The other language is Arabic. Default language of my store is Arabic. I have added and psts-ar.po files in wp-content/languages/plugins folder.
The problem I am facing is it works correct in Arabic language but it displays Arabic even when I select English Language.
Url of page is
Can you please let me know what wrong I am doing?