Can t backup

I have been using the Whatsapp application for a long time, this is the first one on iphone and I have it for about 9 months. so far all the phones have been able to back up whatsapp conversations on this phone just can not. it is connected to wi-fi and it works very well, I have 5gb free in icloud, but it still does not go back up and gives me the error above that tells me to check the internet connection and icloud space. I gave it a restart I tried everything, please help me