Question:

I can not change currency on my site after the first currency's selection.


Answer:

We have checked and found that the root of the issue is due to the currency rate is not updated after the extension is installed.

Could you please have a look on the screenshot below for reference?

For more information about product, please refer Checkout with Display Currency for Magento 2 page.

If you need any further assistance, please feel free to contact us.
Please visit our site for more useful Magento 2 Extensions: https://bsscommerce.com/magento-2-extensions.html