If you use SQL Backup to URL to backup your databases to Azure blob storage remember that for the container name case is important

So

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BACKUP LOG [DatabaseName]
TO URL = N'https://storageaccountname.blob.core.windows.net/containername/databasename_log_dmmyyhhss.trn'
WITH CHECKSUM, NO_COMPRESSION, CREDENTIAL = N'credential'

will work but

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BACKUP LOG [DatabaseName]
TO URL = N'https://storageaccountname.blob.core.windows.net/CONTAINERNAME/databasename_log_dmmyyhhss.trn'
WITH CHECKSUM, NO_COMPRESSION, CREDENTIAL = N'credential'

will give an (400) Bad Request Error which may not be easy to diagnose

Msg 3271, Level 16, State 1, Line 1 A nonrecoverable I/O error occurred on file “https://storageacccountname.blob.core.windows.net/CONTAINERNAME/databasename_log_dmmyyhhss.trn':" Backup to URL received an exception from the remote endpoint. Exception Message: The remote server returned an error: (400) Bad Request.. Msg 3013, Level 16, State 1, Line 1 BACKUP LOG is terminating abnormally.

If you are using Ola Hallengrens jobs to perform your backup then your job step will look like this

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sqlcmd -E -S $(ESCAPE_SQUOTE(SRVR)) -d DBA-Admin -Q "EXECUTE [dbo].[DatabaseBackup] @Databases = 'USER_DATABASES',  @URL = 'https://storageaccountname.blob.core.windows.net/containername', @Credential = 'credential', @BackupType = 'LOG', @ChangeBackupType = 'Y', @Verify = 'Y', @CheckSum = 'Y', @LogToTable = 'Y'" -b

Note the @ChangeBackupType = ‘Y’ parameter which is not created by default but I think is very useful. If you have just created a database and take log backups every 15 minutes but differential (or full) every night the log backup will fail until a full backup has been taken. This parameter will check if a log backup is possible and if not take a full backup meaning that you still can keep to your RTO/RPO requirements even for newly created databases