I am out of ideas, sorry. When there are more reports (currently yours is the only one) I'll probably be able to find out what causes the problem. Or, hopefully, this will start working for you as it did before.
2 years ago(+1)
I've found exactly the same problem - creating city/town maps for a small island, and downloaded the first 2 no problem, but the 3rd has this exact issue - clicking "export as png" either in the menu or via right click just shifts the map to the left on the screen and doesn't attempt to save it. However, saving one after this had no trouble.
The link to the map that I'm having trouble with is below. I used Azgaar's map generator which loads seeds for each city.
https://watabou.github.io/city-generator/?size=24&seed=1310050910026&name=Durnum...
It looks like something breaks on some step of exporting the map (either when creating a hi-res version of it, or while writing it to a file). Have you checked your browser console? It's just odd that this doesn't cause any messages there. And the problem is that this city of your is exported normally for me...
2 years ago(+1)
Apologies for the delay replying -
The export to png works for this town in Chrome and Edge - it doesn't work consistently in Firefox.
I've put an image of the console output when it fails on firefox - hopefully this is useful for you!
OK, for some reason this log doesn't look as readable as it should, but I'm pretty sure the generator breaks because the exported map is too large (in pixels, not in meters, buildings or anything like that). I'll try to come up with a fix for it without sacrificing too much of image quality. Thanks!