I use TD Trader App on my phone and TD Trade Architect on my laptop. Im new as well and i learned this morning you cant day trade on TD. I think you get a total of like 3 trades in a 5 day period. And, unless you have a margin account or only trade a small percentage of your "available cash for trading" youll only be able to do one trade until your "unsettled cash" clears.

Which takes 1 to 3 business days. I only funded 200 and used 180 on a trade so i cant trade until my unsettled cash transfers back into my available cash for trading. Just gotta learn as you go i guess because some people forget to include small details