Hello @MeghanO045 ,
It seems to be an odd, intermittent issue that our engineers are looking into. I've assigned your case to them for review while they investigate. If and when they have an update, they'll make sure to reach out.
Normally they'd recommend downloading the PDF variation, and then using a 3rd party system to convert it to a PNG. Since the PDF variation isn't available to you, it looks like the only option is JPG.
If this issue persists on other campaigns for you, please let us know so we can update as needed.