I can't acces my icloud storage

Same issue here, exactly as shown in your screen capture. But it happens on one of my Windows7 machines, not on the other. That points to some conflict between iCloud and another piece of software, or some problem/corruption with some of iCloud's data on that machine. (It *probably* rules out a server-side issue.)

But I have checked everything I can think of, and can't find what's different between the two machines. I've uninstalled/reinstalled iCloud multiple times. I've uninstalled antivirus, turned off firewalls. I've reset winsock, flushed dns resolver. I've logged all devices (including the PCs) out of iCloud, then logged them back in. I've created an entirely new user profile. And this happens with two different iCloud accounts (mine and my wife's account). Still get the "empty" dialog on one machine, just as shown in your screen capture. Both work fine on the other machine.

In addition, if you maximize that window -- and then click the "Buy More Storage" button, another error is displayed: "An error occurred validating your storage server credentials."

I am having the exact same problem on Windows 10. I also keep getting the error message that my iCloud is almost full. Comes up every 5 or 10 minutes. Very obnoxious.

Try uninstalling, reinstalling, restarting and other combinations.

Please fix.

@timwr19 - Is your iCloud storage really full? Or is there some "extra" backup space consumed? After upgrading devices to iOS9, I noticed our accounts (mine and my wife's) both showed more backup space consumed than the total of the backups themselves. It's as if there was an "old", unlisted backup still taking up space. For example, mine listed the new iOS9 backups for my three devices, which totaled 2.3gb, but iCloud said backups were taking 3.4gb.

I fixed THAT problem (the extra backup space missing) on MY account by doing the following:

1 - Turned off iCloud backup on all devices.

2 - Deleted all iCloud backups (with all backups gone, iCloud still said there was 1.1gb being used by Backups).

3 - Signed all devices (and PC) out of iCloud.

4 - Connected each device to iTunes and backed up manually to PC.

5 - Signed each device back into iCloud, and performed a backup to iCloud.

For MY account, as soon as I signed the first iOS device back into iCloud, the "missing" 1.1gb of space was immediately recovered. iCloud then correctly said there was NO space taken by backups. All three devices backed up correctly thereafter.

Unfortunately, that sequence (and I repeated it twice) did NOT fix the problem on my wife's account. The total backup space consumed is still greater than the total size of the backups.

And the other problem -- the one posted here by original poster -- still persists. Cannot see iCloud storage details, or get to "Buy more storage", from iCloud for Windows.

Thanks Scott, I'll give that a try. I remember having to do something like that a while back.

It would be nice if Apple made our lives a little easier by letting us truly manage our backup storage instead of asking us for more money to cover "phantom storage".

I just installed iCloud for Windows v5, just released by Apple, and this problem is fixed for me. The storage dialog displays correctly again! (I'm running Windows7, YMMV).