Setting a production database to simple recovery is a bad idea, as it will affect your backup strategy and you won't be able to do a point in time restore.

When you run DBCC LOGINFO, you will see that the column status has values of 0 and 2. If there are 2s at the end of your log file, you won't be able to shrink it.

A way to go around is to choose a small clustered index, and rebuild it multiple times. That will start moving the 0s to the end of the file and when you run DBCC LOGINFO and see 0s at the end, you should be able to shink it.

I would put my index rebuild command into a loop of like 100 times and then check the output of DBCC LOGINFO when rebuild is done and if its 0s at the end then shrink should work.