I'm with Ameritrade but also with Etrade. You can purchase with Etrade, as I did yesterday, but not Ameritrade, although they let me buy my first 3,000,000 at Ameritrade. Something wrong there at Ameritrade. But it was quite awhile ago I bought through Ameritrade.
TD Ameritrade is the canary in the mine. It is always the first one to "protect investors" by restricting purchases. Etrade is often right behind. I was able to put a buy order in at Schwabb but they are usually a week or so behind in restricting a stock.
I would say something is going on and caution is called for when this starts to happen.
I am still long and have my sells set high, not trying to get out but rather to make a huge profit. I feel better about GDTK today than I have in many months.