Cannot shrink transaction log
Check your output for DBCC LOGINFO within the context of your database.  This will show you the status of all VLFs within the log file.  You shrink operation will not reduce the log file past the last active one (Status=2).  As VLFs are used in a sequential, round-robin fashion, you will need to run transaction log backups enough times until your active VLFs are at physical point in the file that you want to shrink to.

While you state the database is not very active, transaction log backups once a day seem very infrequent and, depending on the kind of transactions that run against this database, could be contributing to the continued growth of this database.  I would recommend running your log backups at least hourly.  If you don't need this kind of recovery in your database and just need to restore to sometime in the last 24 hours, I suggest you convert the database to SIMPLE mode and do a full backup once a day.

Mike Walsh provides a detailed explanation here.

Your reindexing will do very little to actually shrink or allow the file to shrink and, in fact, may hamper it.  This is because reindexing will create additional transactions in your log that will be active until you run a log backup.

Additionally, some best practices recommendations:


Turn off autoshrink.  This is an incredibly bad practice for a number of reasons.  You are likely creating more problems for yourself by enabling this "feature".
Do not ever use truncate_only.  This basically makes your log useless for purposes of recovery.  You might as well go with SIMPLE mode and full backups at this point.