Decryption fails running iOS 14.2

Simply, go to the App Store and re-download Dropbox. No need for Customer Service.

Same here. Password protected Word doc "Decryption failed (null)" will not open.

I have the same issue. I am on iPhone 8 running iOS 14.2.

Get the "decryption failed (null)" message, and it looks like an iOS issue. To overcome the problem, I installed Excel, signed in and click on the "Open" blue button on the "encryption null" screen on Dropbox and it opens the relevant file (Excel, Word, PowerPoint) in the Excel, Word or PowerPoint app. Enter the password and it unlocks the file.

It's not seamless as opening it from the Dropbox app, but it allows to view (and edit) the file to say the least.

I'm experiencing the same problem.  I found that going back to the original Word document, and resaving it as a .doc file (not .docx) is a workaround.

When you do this, you may get a warning that .doc file encryption isn't as strong as .docx encyption; I think that could be a clue to what is happening, and the problem is that ios14.2 has a problem with the stronger encyption.  But falling back to .doc is a temporary workaround until Apple fixes the problem.

I did what others have suggested as a work around until DropBox fixes the problem.

My password protected files in DropBox are all Excel Files.  They open just fine with the passwords on my desktop but not on my phone.  I downloaded the Excel app on my phone.  I gave it permission to link to DropBox files on my phone.

I can now open them in the Excel app (with the passwords) just as quickly and easily as accessing Dropbox. And the files can be emailed/copied/saved from Excel.

I hope your files can be opened with an app that you can do this same work around with.

I have updated to apple software to 14.2.  I am trying to open a file that is NOT encrypted, and I get a message that "decryption failed. null."  Can anyone help me?