You will only gain shared party XP if you are visible to the player gaining XP

src/main/java/com/gmail/nossr50/party/ShareHandler.java

@@ -35,7 +35,7 @@ public final class ShareHandler {
             return false;
         }
 
-        List<Player> nearMembers = PartyManager.getNearMembers(mcMMOPlayer);
+        List<Player> nearMembers = PartyManager.getNearVisibleMembers(mcMMOPlayer);
 
         if (nearMembers.isEmpty()) {
             return false;

src/main/java/com/gmail/nossr50/util/player/NotificationManager.java

@@ -32,7 +32,16 @@ public class NotificationManager {
         sendNotification(player, customEvent);
     }
 
-    public static void sendOtherPlayersSkillInfo(Player source, NotificationType notificationType, String key, String... values)
+    /**
+     * Sends players notifications from mcMMO
+     * This does this by sending out an event so other plugins can cancel it
+     * This event in particular is provided with a source player, and players near the source player are sent the information
+     * @param source the source player for this event
+     * @param notificationType type of notification
+     * @param key Locale Key for the string to use with this event
+     * @param values values to be injected into the locale string
+     */
+    public static void sendNearbyPlayersInformation(Player source, NotificationType notificationType, String key, String... values)
     {
         Location location = source.getLocation();
         for (Player otherPlayer : source.getWorld().getPlayers()) {

src/main/java/com/gmail/nossr50/util/skills/SkillUtils.java

@@ -137,7 +137,7 @@ public class SkillUtils {
 
         for (Player otherPlayer : player.getWorld().getPlayers()) {
             if (otherPlayer != player && Misc.isNear(location, otherPlayer.getLocation(), Misc.SKILL_MESSAGE_MAX_SENDING_DISTANCE)) {
-                NotificationManager.sendOtherPlayersSkillInfo(player, notificationType, key);
+                NotificationManager.sendNearbyPlayersInformation(player, notificationType, key);
             }
         }
     }