HD 7970 Not Working

I want to use my old computer, which I built back in 2010 and whose HD 5870 I upgraded to an Asus DirectCU II HD 7970 in 2013, for cryptocurrency mining until I get a better card for that purpose (I have a GTX 1080 Ti in my most recently built machine but don't want to wear down said machine by using it to mine).

However, even though my display appears to detect the 7970 whenever I turn on my old computer, which it does by prompting me to switch to the input channel to which I have my old computer connected, the 7970 displays absolutely nothing and therefore causes my display to show a notification that says "No Input."

I know that the problem is the 7970 and not the old computer itself, because the old computer's video output works perfectly whenever I connect my HD 5870 to it. Furthermore, when I swap my 7970 with my 1080 Ti in my most recently built computer, it still fails to provide a video signal.

I don't understand why it's doing this, because when I decommissioned by old computer a year ago and placed my 7970 into its box, the card was working perfectly fine. So, I don't understand how it could have become damaged or defective since then.

By the way, the LED indicators above my 7970's power-connector sockets glow green and both the card's fans spin, which indicate that it's functioning and isn't dead.

So, what do you guys think is the problem?

Just because the green lights glow doesn't mean it's working, just that it has power afaik. GPUs can still die in storage, There's still going to be some stress from temperature changes to cause a malfunction, usually a solder crack between the GPU and the board. Could also be static, but realistically there isn't much that can be done to bring it back to life. Things like baking are only temporary.

It was inside an anti-static bag for the entire time that it was in its box.

I removed the backplate and heatsink and then cleaned off the PCB with a compressed air canister. However, the card still won't post.

@omni-gamer: Its probably toast.

@_SKatEDiRt_: I've pretty much given up on the card and have accepted that it's dead; I've been in denial. However, I'm perplexed as to how it died while in storage; it was working perfectly when I decommissioned it.

@omni-gamer: So far ive had 4 cards die in storage so you are not alone

@_SKatEDiRt_: Maybe putting cards in their boxes after they've been used extensively is the problem, because when I decommissioned my HD 5870, which I've had since 2010, I never put it back into its box but have kept it atop my media shelf as a display piece and it still works.

@omni-gamer: I have no idea that might be. The cards that have survived had been subject to all kinds of physical abuse. Some are just tougher than others.

I've pretty much given up trying to explain why computer components sometimes do what they do.

Example: last time I attempted to do SLI, my PC wouldn't post at all, until I merely switched the two cards around in their slots. That was the only change. I even changed them back afterwards, confirming all of the power connectors were hooked up etc, same thing.

Maybe both cards were into BDSM and I attempted to put the top on the bottom and vice versa? :P

I've had components die in storage and have had friends who have had the same thing happen as well. The worst culprit i've seen is motherboards and it seems like CPU's have been by far the least likely to die in storage