Hi ,
If the "Save Config" button for setting currency is not working, it's possible that there's a conflict with the JavaScript in your Magento installation. Here are some steps you can take to troubleshoot the issue:
Clear your browser's cache and cookies, and try again.
Disable any third-party extensions or customizations that you may have installed, and try again.
Check if there are any JavaScript errors in your browser console. To do this, open your browser's developer console and look for any red error messages that may be related to the currency settings page.
If you're not seeing any JavaScript errors in the console, you may need to debug the JavaScript code yourself. This can be done by adding console.log statements in the code to see where it's failing.
If you're not comfortable debugging the code yourself, you may want to consider hiring a Magento developer to help you resolve the issue.
I hope this helps! Let me know if you have any other questions.