P&F Charts sources all of its stock data from the Alpha Vantage service. This is an amazing service which provides a huge range of daily stock prices for stocks, indices and currencies from all over the world. See their website for further information.
It is also important to remember that AlphaVantage update the daily prices sometime after the close of trading for a specific stock. If you want intraday data, try using an intraday interval (e.g. hourly). You can change this on the Parameters screen for a specific stock in your watchlists.
However, it sometimes (not very often) inexplicably drops a particular stock for some period of time. The search will say they support it (and probably did until yesterday) but will report no data available when asked for the latest prices. Unfortunately this is completely out of our control and Alpha Vantage unfortunately does not have a support capability that can answer questions about particular stock price availability. If this happens to you, please keep trying as they often come back in a few days.