When you're using a Microsoft IIS server and FastCGI and you're unable to upload big-size audio or video, it is most probably hitting a time limit issue. So, to fix this issue, you'll need to increase the time limit in the server setting. Refer to the following steps to help you set up this.
If you're using Nginx server, please refer to Unable to upload audio/video on nginx documentation.
Login to your cPanel and locate the FastCGI Settings.
Right-click and select Open Feature from the dropdown option.
Select the FastCGI application and choose Edit from the dropdown.
Set the Activity Timeout option to a longer time.
If you are unsure how to do this, it's best to contact your hosting provider for clarification.