URL: https://mega.nz/#!j7x0wQDR!j7YAxYNDxILDgpdpZaQrEIC_SphjObeyaG54BU4J-V8

Browser / Version: Firefox Preview 2.0.0
Operating System: Android
Tested Another Browser: Yes

Problem type: Site is not usable
Description: Can't save downloaded file
Steps to Reproduce:
Once the page loads, tap on "Download" and wait for progress bar to fill up.

Tap on "SAVE FILE", then "Download" in the pop-up.

A toast message will appear saying that "Firefox Preview can't download this file type."

Downloads fine in Firefox for Android app or via other sources (same file type).

From webcompat.com with ❤️