DBCC LOGINFO shows the extends not empty into your log file. Shrink commands will only work when you have NO entry on the log file extends marked as 2 (in the head of the file)....

If you want to knock down this 40GB ldf, then follow below steps:

Option 1 (saving the trn files)

1 - Take transaciotn log backups till your DBCC LOGINFO gets all extends with 0

2 - Run the shrink command as the extends are now free and the head of the ldf file is oka to be shrunk.

Option 2

1 - Run a backup with truncate_only to your database

2 - Shrink the log file

3 - run a full backup of your database otherwise All other backup log will fail!

Regards,

Marcos Rosa