Unable to delete file in iCloud storage

I'm not trying to delete the app. I'm trying to delete the app's backup file.

I've already switched off the app in the iCloud page.

Hopefully a couple of pictures will help

1) Here is the 1.2 GB Viber file in the iCloud storage

(as a side note, I found the reason for the WhatsApp backup issue. Because of the size of the Viber file there is no longer enough space to back up WhatsApp with videos. For now I've excluded videos from the WhatsApp backup and it is now completing normally)

2) The Viber iCloud backup is turned off

3) Trying to delete the Viber backup file from the iPhone Manage Storage simply has no effect. Trying to delete it from the Windows App gives the following error.

Thanks

No. I haven't tried that as it seems that it's more of an iCloud storage issue (because the delete doesn't work from the Windows App either).

Also, without the backup working, I don't want to lose all my chat history.

I don't backup the phone to iCloud but I do back up Viber and WhatsApp from the options in those apps to iCloud (though I now notice that the WhatsApp backup doesn't seem to be working either, it seems to stick after only 15mb).

It's the Viber backup file that seems to be be corrupt.

I back up my phone locally, to iTunes, but I can't remember if the last time I got a new phone the restore included the chats or not.

I've changed my Apple ID as per the Apple Support instructions so that my account is now using a gmail address, rather than an iCloud address.

Unfortunately the attempts to delete the corrupt Viber file still give the same results. Is there something else I should be doing now that I've changed the Apple ID?

I don't backup the phone to the Cloud.

Settings > Name > iCloud > Manage Storage > Backup is empty

Settings > Name > iCloud > Manage Storage is where the corrupt Viber file is.

Yes. For certain apps. Not for the whole phone