Buffs on the Fan Chart?

There were some a while back. I guess they got fed up Nomura-kantoku.

But to answer your question, yes, it is because there are no registered Orix fans. I checked the database directly:

+-----------+-------+
| fav_team  | count |
+-----------+-------+
| HT        |    33 |
| CD        |    13 |
| YBS       |     4 |
| TYS       |    13 |
| YG        |    12 |
| HC        |     7 |
| CLM       |     8 |
| FSH       |     8 |
| SL        |    12 |
| HNHF      |     5 |
| TRGE      |     2 |
+-----------+-------+

As you can see, only 11 teams are represented.

To make sure that the Buffaloes are selectable, I temporarily selected them as my favorite team and got this result:

+-----------+-------+
| fav_team  | count |
+-----------+-------+
| HT        |    33 |
| CD        |    13 |
| YBS       |     3 |
| TYS       |    13 |
| YG        |    12 |
| HC        |     7 |
| CLM       |     8 |
| FSH       |     8 |
| SL        |    12 |
| OBs       |     1 |
| HNHF      |     5 |
| TRGE      |     2 |
+-----------+-------+

Yokohama lost a fan and Orix gained one, so it looks like the web application is performing correctly. (Note: The chart is updated periodically, not live, so changing the settings yourself will not be immediately visible.)

It looks like the foreign fan base in Kansai may be swept up with Tiger Fever as the rest of the population is. And with just over 110 people registering a team favorite, the sample size is still too small for such a minor player (who's doing poorly) in that market.