I just upgraded to inDesign 2015 and I'm on a Mac. I have dynamic spelling turned on in the preferences, but it isn't highlighting spelling mistakes. I checked the preferences and I have it turned on and I also check Edit>Spelling>Dynamic Spelling and it is selected.
Is there anything I can do to make it work?
Thank you, Bah
Try refreshing you document by pressing "Shift+F5" command.
On top of this, make sure your language is set to the proper language in character panel. Looks like you have step 1 down. After step 2, you should start seeing your red squiggly lines.