As you may know I have now made 150 svg-designs. Strangely, the last one seems to contain some kind of error that prevents it from generating the proper previews. Also, the image size is not properly detected. I have no clue what's wrong with the file. Could you have a look at it, and maybe find out what's wrong with it? The file I'm talking about is:
I don't think there's anything intrinsically wrong with the file itself. The W3C validator gives one error, concerning the use of the <author> element (which apparently doesn't exist in SVG), but that can't be the culprit, as most of your files seem to have it.
The actual issue is the same one as I think the NYC flag I deleted last month had: the wiki's SVG renderer choking on an exceedingly large path element (confirmed by uploading a version that removes the troublesome path altogether). The main part of the lion is a 175-kB path with over 3,900 nodes.
Oddly enough, the SVG of the current flag, which uses the same lion with the same large path, renders correctly. I have no clue what the difference between the two is that makes your file fail; the one thing I could think of is that yours has the path in two nested groups (<g>) with a transform on them, but removing the transforms by ungrouping and regrouping didn't help. I'll just try simplifying the path and/or breaking it into parts to make it work.
Thank you for researching this. I will resolve it by replacing the much too detailed lion on this flag by the much simpler (but heraldically equal) one on the shield of New Brunswick - that should fix it. It will reduce the file size dramatically, and as an added bonus have a more stylized (and thus more modern) look.
I reduced the number of nodes to 720 by cutting out some of the "overnoded" sections (mainly along the paws and chin), using Inkscape's "simplify path" on each of them, and reattaching. I also removed a redundant copy of the upper half that was there for some reason (which the original flag also has). It works now.
No problem if you decide to replace the lion altogether (I didn't see your reply before uploading the simplified version); the "fixed" lion can be used on the current flag's SVG, or maybe even the Wikimedia original.