What criteria determines if a stock is tradable or untradable on Alpaca?

Some stocks have been bought by my algorithm, but when the price has reached my sell criteria the action will sometimes return as “not tradable.” Does anyone know if this is due to a lack of price data, or possibly the fact I am trading low priced and low volume stocks?

I’m using pylivetrader, and zipline. I check for tradability with if(data.can_trade(stock)): , a zipline function.

are you using “LIMIT SELL” orders ?

No, I will give it a try. Thanks.

i use market orders for the selling side and a limit order for the buy