Hi there,
Apologies for any inconvenience caused. It seems like the file might be corrupted, although you mentioned experiencing this issue with multiple files. Could you please confirm the version of Illustrator in which these files were created, as well as the version you're currently using? Additionally, please let us know where these files are saved (Network Drive/System HDD/Shared Folder on System/External HDD). We'll do our best to assist you!