Error opening excel file in SharePoint online

I'm using SharePoint Online and Excel 2013.  I've been able to repeat this with several files and another user.  The Excel file is in a document library in SharePoint.  When I open an excel file it will show as Read only.  I can then click Edit in Excel or Edit in browser and make an edit.  

Then, if I select Edit in Excel either the file will not open (or takes a long, long, long time) or it says the file is locked by me and gives me several options such as downloading a local copy.  When I go back into the file after that, I can then edit in browser but it shows me in twice and again, it shows locked if I try to go into Edit in Excel.  

Until yesterday, I've had no problem with Excel file sharing so I'm baffled by this and think it surely must be something right in front of me that I'm missing!   The file does show checked-in in the library view and there are no required fields on this library.  

Any ideas?  This same exact behavior is occuring with two other users that I'm aware of.  The one who asked for help, me and then another person who I'd asked to see if she was getting the same behavior.

Thanks for any ideas that might be helpful!