sops: Cannot get Azure Keyvault example to work

Hi!

I am trying to follow the Azure Keyvault example (https://github.com/mozilla/sops#encrypting-using-azure-key-vault) but cannot get it to work. I have redone the example several times but always end up with this error:

[AZKV]	 ERRO[0030] Encryption failed                             error="azure.BearerAuthorizer#WithAuthorization: Failed to refresh the Token for request to https://sops-XXXXXX.vault.azure.net/keys/sops-key/XXXXXXX/encrypt?api-version=2016-10-01: StatusCode=0 -- Original Error: adal: Failed to execute the refresh request. Error = 'Get http://XXX.XXX.XXX.XXX/metadata/identity/oauth2/token?api-version=2018-02-01&resource=https%3A%2F%2Fvault.azure.net: dial tcp XXX.XXX.XXX.XXX:80: i/o timeout'" key=sops-key version=a114809b9efe4b7286aa67317a5e5ccd
Could not generate data key: [failed to encrypt new data key with master key "https://sops-XXXXXX.vault.azure.net/keys/sops-key/XXXXXXX": Failed to encrypt data: azure.BearerAuthorizer#WithAuthorization: Failed to refresh the Token for request to https://sops-XXXXXX.vault.azure.net/keys/sops-key/XXXXXXX/encrypt?api-version=2016-10-01: StatusCode=0 -- Original Error: adal: Failed to execute the refresh request. Error = 'Get http://XXX.XXX.XXX.XXX/metadata/identity/oauth2/token?api-version=2018-02-01&resource=https%3A%2F%2Fvault.azure.net: dial tcp XXX.XXX.XXX.XXX:80: i/o timeout']

I am following the instructions step by step, I even tried creating a new resource group and a new service principal, but that didn’t work either. I also set the environment variables specified in the instructions to the values provided by the service principal. Any ideas what I’m doing wrong?