Cannot complete iCloud backup

Every time I try to back up my iPhone X through iCloud, it gives me the cannot complete backup message because there's not enough storage. I've only used 9.6 GB of my 50 GB of storage, even upgraded my iCloud storage last year so I would have enough room. I've deleted photos, videos, texts, voicemails, removed apps from iCloud, deleted apps from my phone, but nothing will work.

I cannot back up to my Mac because there's not enough computer storage available there either. I need the backup to complete so I can upgrade phones!

Any advice!!