Hi,
Here is a [http://support.hp.com/au-en/product/hp-envy-m6-1200-notebook-pc-series/5330543/model/5359749/document/c01732674#AbT2|link] that describes what the LED codes mean.
Select ''LEDs near Caps Lock and Number Lock keys blink when starting the notebook'' and then select ''BIOS flashing light error codes for computers released between 2011 and 2015'' to find which error is being displayed.
Your RAM slot being loose is not a good sign. Try using just the one good RAM slot (you say one is loose that implies that there are others) and see if the laptop starts.