Hello,
I could really use your help.
I don't speak English very well, so I'm using Google Translate to translate this message. I hope that's okay with you all.
 
I had imported my sheet music (is it the right word?) I call it songletters from Google Drive onto my iPad using the Mobile Sheets app.
Now, I have edited the  on my iPad. Since I only have 5 GB of storage on Google Drive, I would like to back up my Mobile Sheets data to my OneDrive account instead. So, I installed the OneDrive app on my iPad.
 
Now, regarding the backup process: I followed the steps, but the file isn't actually uploading. I don't know why.
 
I navigate to Settings > Backup and Restore > Backup Library, and under "Drive," I select "Local Drive." I leave the default filename as is and confirm by tapping OK. I tap OK once more. I can see my sheet music files/songletters files being compressed very quickly. Afterward, I am able to select my OneDrive account on the left, choose a specific folder, and initiate the backup. At this stage, I see a faint entry for my file labeled "Error." If I try to back it up again, a message appears after just one second stating: "Backup successfully completed. File written to [file path]."
 
What am I doing wrong? Why isn't the file uploading?
 
My mobileShetts Version: 3.9.41
 
Thanks a lot for your tips!