iCloud backup for whatsApp

Today my WhatsApp informed I was no more able to use it, and I had to 'buy' a new one in AppStore.

After multiple tries, I deleted the WhatsApp, and re-downloaded a new one. Entered my phone number and ID, and tried to restore from my last WhatsApp iCloud Backup (11/05/2020) which informs having 15,5GB. Well enough as my iPhone XR IOS 13.4.1 has 37GB used of 128GB and my iCloud has 88GB from my pack of 200GB. The info in WhatsApp is that it is unable to restore from iCloud. Keep trying and same message always...

Any help on this ? Is this an iCloud issue, or a WhatsApp issue ?

Thanks, Pedro