HelloT omKomalski,
Thank you for using Apple Support Communities. Sound like you're unable to update a file to your iCloud Drive but it never completes the task and nothing gets uploaded. If so, we'd like to recommend some steps to help sort this issue out. Let's follow the steps below to further isolate this issue:
1.) Restart your iPhone to help refresh things.
2.) Test under a different reliable Wi-Fi network. This step can help isolate a possible network related issue.
3.) Try uploading a different file. If issue only occurs with one specific file, perhaps that file might be corrupt but this step will help get a better idea if that's the case.
4.) Remove any VPNs that might be installed on your device. VPNs can sometimes interfere with communicates with iCloud.
5.) Make sure you don't have any new available updates for you iPhone. If you do have a pending update, it would be best to install it. This can usually help with unique issues, since updates include fixes. Just in case, this link can guide you through the update process: Update your iPhone or iPad - Apple Support
1.)Back up your device using iCloud or your computer.
2.)Plug your device into power and connect to the internet with Wi-Fi.
3.)Go to Settings > General, then tap Software Update.
4.) If you see more than one software update option available, choose the one that you want to install.
5.) Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now. If you don't know your passcode, learn what to do.
We hope these steps help you out. Thank you for using Apple Support Communities. Best of luck.