Excel file format is not valid. Please help as unable to open Excel.

I think I found the solution. If you disable the office dropbox add-in the problem doesn't seem to occur anymore. You can still save to dropbox via file explorer making it redundant anyhow. to do this, open excel, go under file, Choose "Options", and navigate to "add-ins". From there locate the Dropbox Add-in and right click, select "disable". Should stop it from being an issue.

Issue with Excel - "Excel file format is not valid"

Rich
Super User II
8 years ago
You need to provide more information about the problem you're having. Are you opening Excel files from the Dropbox folder on your desktop, or the Dropbox website? Does the problem only occur with files in your Dropbox folder, or elsewhere on your computer as well? Have you dragged one of the problem files out of your Dropbox to your desktop and tried to open it from there? Mac or PC? Office version? etc.
- flew
  Explorer | Level 3
  8 years ago
  I am trying to open Excel from both but neither are opening. Desktop error says "file format is not valid". I edited the document on 2 September with no issues.
  - Jane
    Dropbox Staff
    8 years ago
    Hey flew,
    
    Hmmm... Mere guess here, since I've encountered the same error in the past.
    
    If it's an .xls file, you'll probably need to modify (:repair) the file extension to .xslx. If you run a google-search, you'll easily find some articles that will walk you through the process as well.
    
    If this persists, would you mind including a screenshot (omitting personal info) of what you're seeing in your next post here, so that I check it with you?
    
    Thanks!
- Brandos
  Helpful | Level 6
  8 years ago
  The issue happens when a user uses the dropbox office 2016 add-on to do a save as function in excel 2016 directly into dropbox.
  
  Example: Someone sent me a .csv I open it in excel 2016 but would prefer it be saved as .xlsx . If I choose save as the dropbox option is displayed at the left. with the add-on. If you select this and change the file format it saves to dropbox in the original format and only changes the file extension. Causing the file to appear corrupted. If you do this process in any other way either with competing cloud storage or just through file explorer it is fine and works as expected.
  
  That is the nature of the issue. Noted in windows 7, windows 8, and windows 10, excel 2016 365.
- Brandos
  Helpful | Level 6
  8 years ago
  I think I found the solution.
  
  If you disable the office dropbox add-in the problem doesn't seem to occur anymore. You can still save to dropbox via file explorer making it redundant anyhow.
  
  to do this, open excel, go under file, Choose "Options", and navigate to "add-ins".
  
  From there locate the Dropbox Add-in and right click, select "disable".
  
  Should stop it from being an issue.
  - lbarry
    New member | Level 2
    6 years ago
    I have been using my dropbox account for a few years with no issues. Recently, when I was saving a file (which Iregularly use) a message popped up saying I needed to "grant access" to save the file to the location. It was a random message that had never come up before but I granted access and was able to proceed. This has appeared a few times for different files since then.
    
    Now my lastest issue is that it won't let me open a file. The error message states:
    
    "Excel cannot open the file 'George Cycle 2.xlsx' because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file."
    
    I use these files regularly and this has just come out of the blue.
    
    All ideas as to why this has started happening would be great!!
    
    Thanks!