Dear respected Julie,
Good day! Thanks for posting in our community.
We went through your post carefully and deployed some tests with Sway newsletters created before and newly. As we failed to upload to reproduce it on our machines, to offer you the correct guide to resolve this, could you please share us some more details as troubleshooting steps below?
- Could you please check the behavior from various browsers and other PCs. Even a browser from mobile phone can via access sway.office.com to see if the newsletter can open correctly.
- Since I noticed you post in For Business category, we would like to know if it is possible for you to confirm with other colleagues in your company and see if they will see a same behavior which may indicate the issue is from tenant side?
- Please share us a complete screenshot of the error message page for further troubleshooting.
We appreciate your kind patience and understanding that sometime the initial reply may not resolve the concern immediately or there may have some misunderstanding about your scenario, but we would like to hear the updates from your side and let's figure out the further suggestions.
We'll be here for you to wait for your updates. I appreciate your time and effort on checking these above and thank you for your time and cooperation. I hope that you are keeping safe and well!
Sincerely,
Mia | Microsoft Community Moderator