I’m trying to change some settings, and when hit save button, the changes don’t saved.

Caching does not work! You don't have permission to access ...

This issue is most commonly caused by wrong file permissions. Your uploads directory should have correct file permissions otherwise WordPress will not be able to store your files in it or sometimes may not even display files from the upload directory. To set correct file permissions for your uploads directory, you would need a FTP client, like Filezilla. If you see warning like this you need connect to your website using the FTP client and then go to /wp-content/plugins/festi-woocommerce-cart/ directory. There you will see /plugins/festi-woocommerce-cart/. Right click on the uploads directory and select file permissions. 

A new dialog box for file permissions will open. At first you will need to set file permissions for uploads directory itself and all the sub directories inside it to 777.

To do that, enter 777 in the numberic value box, and then check the box next toRecurse into subdirectories.

Lastly, you need to click on 'Apply to directories only' radio button.

Click on the OK button to apply these changes. Filezilla will now start applying file permissions to the directories.

Filezilla will now set the file permissions for all the directories Once it is done, you can go back to your WooCart Pro Settings and click on Refresh plagin button.

After refreshing you will see success message: