Are you on windows 11?
So, it's not just Dropbox that has the icon.... the 0 bytes indicates it in not synced, that it's just the pointer (shortcut) to the file online. If you double click (and are signed into the account and online), it should download then open. If it's not opening, I would sign out of OneDrive, rename the OneDrive folder then sign back in and let it sync everything again.
For one reason or another, windows won't / can't display the online icon - one theory I found this morning is the file attributes are corrupt, so it shows that icon. It makes some sense since only the shortcuts to the online-only files have the icon. But the attributes look fine to me and changing them did not fix the icon.
My OneDrive files are fine - it's the dropbox one with weird icon.
