Toggle output lines on a PIC24FJ64GB110 processor
Check whether that pin is a A/D or comparator input.  On reset, all pins that can be analog inputs are configured that way.  To use them for digital I/O requires configuring them to digital.  Different PICs do that different ways.  Take a look at the applicable A/D and comparator chapters of the family reference manual to see how to make analog-capable pins digital.  To find the right family reference chapters, look in the datasheet for your particular part.  Each peripheral will have a brief overview in the datasheet, and the family reference manual chapter that applies to that peripheral will be listed at the beginning of the datasheet chapter.

Until you get things working, try using the pin in regular push-pull output mode.  You can use open drain later once you get it working.  For now, that just adds another possibility for screwup.