Thanks for posting about this and for your patience with this issue.
I wanted to update you with our team’s investigation:
It looks like the SVG files that aren’t appearing aren’t real SVGs.
Think of SVGs like html files that describe shapes and angles so they can be rendered at any size and any resolution.
This differs from png file that describe every pixel of the image, and cannot be resized bigger without losing information and quality (stretching)
The files that aren’t uploading correctly are using a part of SVG spec to essentially embed a png file inside SVG code.
This may have been caused by the image editing software you used to export the SVGs (e.g. PNG → SVG conversion). You can read more on this here: https://mijingo.com/blog/how-to-convert-an-existing-png-or-gif-to-svg
A relevant snippet from the article:
The simplest way [to convert png → svg] is to use an online conversion tool. But: beware of the image to SVG conversion tools online.
Some of them do not actually convert the image to SVG, which requires retracing the image and turning it into a set of coordinates and lines, but instead just encodes the image as base64. That’s fairly easy to do without needing an online tool and doesn’t help us at all on our goal of creating a real SVG file, not another form of a bitmap image.
We currently don’t support these types of SVG files.
The best solution here is to upload the original png file or a real SVG file. Or to use software like Illustrator to trace the original image to properly convert a PNG to a SVG.