Portal has been working for us, but storage accounts have been unreachable from certain regions for the past 30 minutes. Possibly Portal is also broken in the same regions.
Here in UK it was back briefly but down again, can still use az CLI and tools such as Microsoft Azure Storage Explorer in the meantime thankfully.
Seems to be limited to Europe, or are other regions also affected?
portal.azure.com is down for me as well [EU]. - update: Works again.