Should I enable buying Manually?

There is a trigger to enable buying again that will enable buying on your hopper automatically once the conditions are profitable and favorable again.

You can always disable or enable your hopper's ability to buy on your own whenever you like, as well.

If the hopper doesn't enable buying on its own in a day or so, you can enable it manually if you are feeling good about the market conditions, otherwise you can leave buying disabled until the hopper enables it again.