If you’re being redirected to the dashboard everytime you’re trying to upload your CSV file to the extension this means that you’re exceeding your PHP max upload file size.
There’s two approaches to this, you either need to contact your hosting company and have them make the below changes or if you’re familiar with server configuration make them yourself. It’s worth making a backup of this file before you do anything else.
The file you need to change is php.ini. It’s location depends on your operating system. In a lot of Linux environments it’s found in /etc/php.ini but if you’re unsure Google has many results for this.
The values that need to be changed are:
upload_max_filesize=5M post_max_size = 10M
Change these to a higher value. If your CSV file is 20Mb then change both to around 30M (not Mb!) to ensure they’re uploaded correctly.