I have FME Desktop
FME(R) 2019.2.3.2 (20200320 - Build 19825 - WIN64)
and when I look for 12 amongst the Writers it is not there.
What version of FME introduced the 12D writer?
https://docs.safe.com/fme/html/FME_Desktop_Documentation/FME_ReadersWriters/12dxml/12dxml.htm