You need to have the user rank of "Pentaxian". See
Need More Photo Space? Donation info / Account Comparison (Pentaxian/Site Supporter) - PentaxForums.com
To get that, you have to have either
1000+ Posts and 1+ years' membership and 75+ likes or
300+ posts and 2+ years' membership and 75+ likes. You meet both the post and membership criteria for both of those, but you're lacking in the likes department.
That may have happened to you:
Quote: Note that users who have earned the rank of "Pentaxian" must log in at least once every 2 months, or make a post at least once every 4 months in order to maintain the status. Re-attaining the likes criteria after sufficient forum activity will restore the status.
I think the usual way to regain the status of Pentaxian is to collect enough likes again?