iCloud in zero storage and have 50 gb plan

In my iPad I am trying to make a back up, but since late October I haven't been able to back up.

I have a 50 Gb plan and when I check it on my iPhone I can see there is 37,8 Gb free.

But when I try to check in the iPad, is not able to check storage information.

iCloud account seems to be working fine as well as the credit card info.

What I need to do to solve this?