I'm trying to make previous_post_link() and next_post_link() work inside a custom post type, inside a same category (taxonomy) but its not working.
It this posible ?
I'm trying:
<?php previous_post_link('<div class="posts-next">%link</div>', 'Next in category',TRUE); ?>
I'd suggest using a plugin for this. next_post_link and previous_post_link will use the category taxonomy (literally)*, so they will not work as expected with custom taxonomies, which I think you are using here.
I've used both Smarter Navigation by Scribu and Ambrosite Next/Previous Post Link Plus, which are both great plugins for this sort of thing.
*See the source for get_adjacent_post() which is used by WP's next/previous_post functions in \wp-includes\link-template.php to see how "category" is hard-coded.
The taxonomy is no longer hardcoded for next_post_link and previous_post_link you just need to specify it in the last parameter
<?php next_post_link( $format, $link, $in_same_term = false, $excluded_terms = '', $taxonomy = 'category' ); ?>
