Plugin is not changing Currency

Hello
I am having an issue with the plugin when it comes to converting the currency on my site.

first of all it is not auto converting it depending on the user location (right now we have two options canada and USA)

how ever if we do change it manually by using the float bar, sometimes it is changing and sometimes it is not.
and in case the changes has happened it is causing a problem so for example
say that we changed the currency to ($USD) in the shop page , then I moved to a new page which is checkout or cart page the currency is going back to the default value ($CAD)

this is causing lots of troubles when it comes to having orders from USA.

waiting for your response thanks.