I know it will take a while before the website will let you respond to this because you are still in "Newbie" status... I'm just curious if the red light is blinking once every 15 seconds?
If it is blinking once every 15 seconds, it may have properly reset but somehow the pool info is altered or missing and that's the reason it would not be hashing. Then try finding the IP address to log into it so you can set up the proper pool info.
I get what your saying with no problems the past 6 months.
Do you have multiple S5's so you can swap controllers to see if it will work with another controller?