“Can't open the file because the file format/extension is not valid.” error on website/desktop app.

Not a problem, Mitz1!

Did that help you figure out the issue?

If you still need help, let me know what you see when you hover over that icon, so I know the app's sync status and version and assist you further.

Hannah, I didn't realize that was the Dropbox icon.  When I was attempting to reload the DB App over the weekend, everytime it lauched it just gave me a new Dropbox window but without any files. I wish I could go back now and see it that icon was there at the time.

Thanks for your help.

Thanks for the update and the screenshots, Mitz1.

From what I can see on your first screenshot, you do have the Dropbox icon in your system tray.

It's not in the list of hidden icons, it's the one right next to your WiFi icon; can you hover over it with your mouse and let us know what you see?

From the Start Menu, I launched the Dropbox App and this is the window that came up.  I know it’s small, but the tray window bar on the bottom right show that the Dropbox app is not running as there is no tray icon. The syne engine never starts.  I can see the files, but they do not open.

Next is a screen shot is from the Dropbox web. None of these will open from this window. However, on my other laptop I can open all of these EXCEPT the bottom file dated 1/27/2026. That file doesn’t even show up on my other computer. The reason I tried to relink/resync my primary computer was for this reason. Files were missing from the other computer. Something changed around the middle of January and anything that was added after around that date did not show up on computer 2.

It appears to me that during the attempted update, the files were corrupted.

As a side note: Yesterday with the help of a friend, I was finally able to recover at least the file names in my Dropbox folder. I had high hopes that they would open. When I double clicked a file, the first window that came up was that I could not open the file because I was out of memory and it asked me if I wanted to upgrade. I checked my records and confirmed that on June 07, 2025, I had paid $119.88 for an annual Dropbox Plus subscription. Because I was desperate to get that file back, I upgraded to the recommended subscription, which was the same price, $119.88. I received a confirmation email that I had been charged, restarted my computer but none of those files would open and gave me a format or extension not valid error message.

I do not know what kind of support I can expect with the Dropbox Plus subscription. I’m hoping the forum can help me.

Since they fail to open on the web too, the zero-byte placeholder likely overwrote the actual data during that sync crash.

Go to Dropbox .com, right-click one of the broken files, and hit Version History. You're looking for an older version with an actual file size (not 0 bytes). If the only version listed is the current empty one, the real data probably never left your drive before the crash.

Thanks for posting on our Community, Mitz1​. 

First off, I’d like to clarify that we’re not the support team (your support options may differ based on your plan) and we can’t see account-specific info here on the forum. There are still a few things to check together though, in order to determine what may have happened.

Now, can you clarify if you can see the Dropbox icon in your system tray/menu bar at the moment? If the Dropbox app seems to be syncing now, I’d like to know its syncing status.

Other than that, I’d like two separate screenshots of the files you can’t open; one screenshot of what you see on your Dropbox account online and one more of what you see on your desktop app (including any sync icons you may be seeing next to those files).

In general, Dropbox allows you to recover previous versions of files for a specific period of time, which depends on your current Dropbox plan. However, I’d like us to gather a few more details first, to isolate the issue.

Let me know once you have more info.