Listen, TDA does not have it in their vocabulary that this ticker is not a DTC participant. They come up with all kinds of reasons why they can't trade it, from DTC chill to not SEC current. Non-DTC stock was simply not in the reps training manual. You might as well be speaking a foreign language.
That is not the issue, regardless of what you were told. NSAV shares are NOT registered at DTC, and never have been. TDA won't trade any non-dtc registered shares. It is really that simple. Get a better brokerage, like etrade.