Why for the life of me I can’t stay awake when listening to Music?

Two options: 

1. Increased overall fatigue/lower energy due to your age

2. Your system isn't keeping your attention the same way it used to.

And it could be both.

I would suggest a blood test first, check your levels and if you need multivitamins. I am a 53 year old man, and i have had some vitamins and minerals that were lacking, so I got them through supplements. I was feeling the same way you did about 5 years ago, shortly after I retired. 

Now, i have so much energy.... i feel like i am 20 again.

Your system sounds great, so most likely it's just a health-related thing, probably easily fixable. Good luck

I would also recommend a health checkup, even if just to discuss tiredness levels for one's age and activity.

It could be discovered that the Sleep Pattern contributes to the root cause; 8 Hours and an uninterrupted period of REM are very important. Not achieving this will leave tiredness in its wake. 

FTR, I listen to much more CD now, as I like a little cat nap if it creeps up on me .   

It’s your cables. Get Audioquest Coffee and you’ll stay awake.