All emails in folder not downloaded from server

About 6 months ago I moved all my emails from an email account I was losing to an archive folder in another email account. The emails have been accessible in all that time, but for some reason today when I try to access them I get a message for every single email in that folder that they are not downloaded from the server. I can see the emails and subjects etc, but can't read the body of email or access any attachments. Further trouble is I'm now seeing the emails didn't ever sync across devices or to the account , so they only exist on this phone (if I got to the email account online or access the email on another device, the archive folder is empty), so the only way to access them are from this phone. I've reset, tried different connection options, and have 100gb of storage remaining. Is there anything i can do to get these back (they were all available and displaying fine for the last 6 months). I have not deleted/readded the account or sign out/sign in cause the folder seems to only exist in my phone, so I'm worried if I do that and it resyncs with my account it will wipe them completely.