Hi MaryRoberts6,
Thanks for your valuable feedback and share a updates with us. Yes the option is on SharePoint online. Since you are able to attach file in another list (same SharePoint site) with same file from network drive then in this scenario I'm afraid your problematic list got corrected somehow. You may move your column data from problematic list to new created list, here is article for you reference: SharePoint Online: Moving items between lists
I appreciate your understanding and stay safe!!
Best Regards
Waqas Muhammad