SQL Server tempdb log file isn't autogrowing, instead getting error “The transaction log for database 'tempdb' is full due to 'ACTIVE_TRANSACTION'”
This is happening because the disk is full. 

I was given bad information. The primary DBA was out when I had this problem and I asked one of our secondary DBAs to check the disk space on the drive where the tempdb log file lives because I don't actually have access to this server. The secondary DBA told me that there was 25GB free space on that drive. In actuality, there was less than 10MB free space.