pd4ml.useTTF(“java:defaultfonts”, true) would take effect only in a case, if your application includes a JAR with TTF font files placed defaultfonts/ folder of the JAR.

Try to do the following:
1. Upgrade to v398fx1 and test. If it does not resolve the issue, proceed to #2

2. Try to generate a font mapping file for the standard OS fonts: http://pd4ml.com/cookbook/pd4ml_pdf_true_type_fonts.htm
java -jar pd4ml.jar -configure.fonts c:/windows/fonts c:/work/
In the case useTTF() API call should look like that:
pd4ml.useTTF( “c:/work/”, true );
Test it.

3. If the above helped, create a JAR file with chosen fonts, as described by the link above