Just want to update a zip file contents on dropbox

Ok - I have used dropbox for many years to store files that i share content with friends.

I just had a request saying that some of the info in one of the zip files I have shared needs updating.

I have done this before - but not for a few years - no problem just opened the zip file, edited the contents, then upon closing answering yes to do you want to update the zip file contents. But today, it just says "The system cannot find the path specified"

I am using the Desktop App and it does say that it is synced and up to date.

This is causing me a huge problem and significant time and effort for all my files, if I cannot simply edit a zip file on the fly.

I have read that using the PC App avoids the download, edit, upload route - which is not an option, as hundreds of people have the link to this specific file address.

So upset and tired - dropbox used to easily have this function - especially with the PC App and the files being visiable in a window when I use it. Incredibly frustrating to be told i cannot access my own files. Please advise.