Question: Unable to use 2/3 of buying power after stock sale?

I'm quite new to trading so apologies if this is a dumb question.

So earlier this morning I sold a stock that I had been holding a few days when it peaked; when i saw it go back down I thought "yeah I'd get that again".

When I went to click "buy" I noticed my buying power was significantly lower. I checked other stocks and my full buying power was at my disposal, but was limited on this one.

The closest answer I found was "short selling" but as far as I'm aware I never borrowed any stocks.

edit: im using "Robinhood" to trade if that effects the situation

Submitted November 08, 2017 at 12:21PM by Tozai_Senpai http://ift.tt/2iF50cM