I had created a story map 2 years ago and I remember being able to access it and link working till beginning of last year. I hadn't accessed it after and was going to update it for a presentation tomorrw!~
here is the link https://arcg.is/1LyumS
It is supposed to be publicly accessible but it isn't.
Further more, it does not exist in my account!
It was my GIS portfolio and made with firstname.lastname@example.org account.
I had more story maps that don't seem to exist anymore. (https://storymaps.arcgis.com/stories/011d164fd1d1418faddcfcf75c00724a?header&cover=false )
I have stories dating back 10 years or so in both personal (public) and organizational accounts and I have never had a link to a story cease to work. Your link points to a story you have created with ArcGIS StoryMaps and also a story collection. You've not mentioned what type of account you were using when you made your story, but one thing that I can think of is that if you made this using a student account at a university, it's possible that your contents may have been cleared.
I made this using my personal account which is the email email@example.com as my username but that's a good point. I am not sure but I remember having a free membership to use ArcGIS through a non profit organization but I don't see how that would affect my story maps! I have so many other story maps made previously. Only these two made in 2020 vanished!!!
I also want to add that I am trying to make a new story map and I am trying to edit currently and It's showing me the same error message as it showed me for the previous two
@ReginaThomas -- If your account was through a non-profit that you are no longer associated with they may have deleted your content. If you are logging in with different accounts to try to edit your stories you may see that error page if you are logged in with an account that is not the owner of the story you are trying to edit.
I would recommend that you contact Esri Technical Support and they can work with you to help sort out these questions.