iCloud issues can occur for a number of reasons, including after you have upgraded the iOS version on your device. The problems are usually concerned with the iCloud sync. Here are some things you can try to rectify the issue.
1. Sometimes there is a delay in your device retrieving data from iCloud. This can be caused for a number of reasons. The solution is simply to wait for a few minutes.
2. If the data doesn't appear after waiting, or you having other problems with iCloud, you can try turning the iCloud setting for NotesPro off and then on again.
a) Go to Settings on your device and tap iCloud.
b) Tap iCloud Drive.
c) Scroll down to NotesPro
d) Toggle NotesPro off, leave for a few seconds, and then toggle it on again.
e) Go back to NotesPro to check if everything is working and displaying again.
3. If you are still having issues you will need to troubleshoot iCloud. Although iCloud syncing issues are out of our control as they are handled by Apple, most problems can be solved by following the steps below:
a) Check the System Status page for both iCloud and Backup. You can do that here:
b) Check your connectivity to the internet
c) Make sure you are running the latest version of Apple's operating system on all your devices.
d) Set the time automatically. You can do this by going to Settings then General and then Date & Time. You will then see an option to set automatically.
e) Sometimes resetting Documents & Data in iCloud works. Do this by going into iCloud's settings and turn Documents and Data off. Then reset your device before going back into iCloud settings and turning Documents & Data back on again.
f) Reset your documents. This is done by logging onto iCloud on a computer at icloud.com. The process requires several steps which you will need to follow closely. It also involves restarting your devices, but at the end your iCloud data will be reset and merged.
g) If you are using iOS 8.0 or earlier ONLY, try getting iCloud to refresh its Documents and Metadata. Go to Settings > General > Reset > Reset All Settings. Finally confirm the warning.
Note that this should not be done if you are using iOS 8.1 or above.
h) The final thing to try is restoring your device. Create a backup first, but make sure you use Encrypt Local Backup so that all your passwords are saved. Then restore your device before reapplying the backup.