First thing first, make sure you are using Chrome browser,

After you might have input your details,

Tap on the download button. (As usual, an error message pops up)

Now here comes the trick,

Ignore the error message and keep tapping the download button non-stop and consecutively, it will keep bringing the same message but DO NOT STOP TAPPING DOWNLOAD.

You can keep tapping the download button for more than 5 min non stops until you see a download completed pop up on your notification.

The reason for this is that many people are trying to download at the same time, causing the error message.

All you need is patience.

Keep tapping the download button non-stop.