WordPress 4.7.1 was released on 11th January.
It introduced a new bug that stops certain filetypes from being uploaded.
This bug unfortunately stops users from uploading SVGs with the Platform 5 builder.
In the meantime if you need to upload an SVG or have any other image upload issues then please try this plugin that bypasses the mime checks that were introduced.
Link to trac ticket: https://core.trac.wordpress.org/ticket/39550
EDIT: 4.7.2 has been released without the fix. Fix is now slated for 4.7.3