Use Numbers a lot. I'd like to be able to access Numbers spreadsheets on my iPad, but they're in Dropbox, and I can't get the iPad to find a new spreadsheet there. Any hints? Why can't Numbers see the file? DropBox Does.
The only solution I've found here is one that's 8 years old and appears to be irrelevant to current versions.
NOTE: I have both apps, Dropbox & Numbers, on my iPad - and it's an older iPad (Air 2).
iPad Air 2
Unlike some computer Operating Systems (such as Microsoft Windows), iOS/iPadOS does not support opening or editing “in-place” document files are not stored on the device itself, or in iCloud. As such, to open a Numbers files on your iPad, it must first be copied from DropBox (or other cloud storage provider) to your iPad.
Some third-party Apps are available that do support “edit-in-place” functions for some (but not all) document types.
Download the files from Dropbox into files on the iPad. You can then open it. Or, Store the file in iCloud to use it directly in the apps or online
Opening Numbers Spreadsheet on an iPad
