I also created an account in this forum just to share my experience and would like to thank everyone who shared their troubleshooting experiences and insights here to help me fix my issue. (Scroll down to the end for summary.)
I came home from work and tried to turn on the SP3 and it just would not turn on. In the past, the soft-reset and/or force shutdown have worked to fix the issue.
After reading on Microsoft support forums and LifeWire about what to do if the SP3 just won't turn on:
1. I made sure that the SP3 was plugged in and charging with the white LED light lit on the cord. Then let it sit for 15 minutes or so. I was positive that the battery could not have just died completely while I was at work for 8 hours... but just in case.
2. I tried the soft-reset method (hold down power button for 10 secs, release button, and press power button again). That didn't work.
3. I tried the force shutdown method (hold down power button for 30 secs, release button, then press and hold both the power button and volume up button for 30 secs). That didn't work either.
4. I don't have a connected keyboard and was unable to attempt to turn it on with the Windows+Ctrl+Shift+B keys. However, I tried the volume Up/Down numerous times. That didn't work.
5. I disconnected accessories from SP3 and tried to turn it on normally. All I had was a microSD card. That didn't work.
I tried all the steps above several times without any success.
By this time, I did noticed that while I was doing the soft-reset or the force shutdown method, the white LED light on the power did turn on/off accordingly. I was worried that the screen hardware may have failed. After all, the tablet is 5 years old.
Then I found this forum here and read about the rubberband resurrection method, the CPR method, and the USB wake method:
6. I wasn't ready to try the rubberband method just yet since it would take hours to complete. I would do it as a last resort. I simply pushed on the the power button as hard as I could for maybe about 2-5 minutes hoping that it would clear a stuck button of some sort in there. That didn't work.
7. I gently tried the CPR method, not knowing how hard to press on the screen and the back of the SP3. I only pressed hard enough to feel the bend on the screen or the back for a couple times. I even pressed around the corners and edges just in case. Tried to power it up and nothing.
8. Then there was the USB wake method. I don't have an Xbox controller and couldn't follow this route. Then I remembered that I have a USB gamepad around and I figured that maybe I can use it as a substitute for a USB keyboard instead. At the very least, the buttons would simulate some keystrokes of a keyboard. I plugged it in. (I did remember that the white LED light on the power cord was lit while I was doing this.) I pushed all the buttons and arrow keys on the gamepad as if I was entering a secret code into some entertainment consoles like back in the day. Nothing, the screen remained black and dead silent. Then about 5-10 seconds later, the Surface Pro logo was displayed. There was a message saying not to turn off the system as it was trying to complete the Windows update. Once that was done, the login screen was displayed normally.
I figured that while I was away, the system did an update and somehow the process got stuck. The USB wake method shared from this forum woke the tablet and allowed it to complete its update. It saved me $500-$600 from paying for a replacement. Even though it took me about 2.5 hours to get the SP3 back up, I now feel everyone's pain when their Surface tablets won't turn on. Hopefully, this tablet will last me a couple more years before I have to get a replacement.
Summary: Try plugging in a USB cord connected device such as a gamepad, Xbox controller, mouse or even a cell phone to wake up the SP3.
Update:
The day after, the same thing happened again. I tried to use USB cord connected device and it still wouldn't work. This time I used the rubband resurrection method and it worked after about 4 hours. I was able to save all my data. I also updated the BIOS to allow for USB boot in case I needed to take this route in the future (it was disabled). I suspected that there is an issue with the wake from hibernation process. I disabled the hibernation function and so far it has worked well. That night right before powering down, it performed another Windows update. I was a little worried and wondered if a recent update caused this issue. The next day I turned on the SP3 and it powered up just fine. So far, no further issues.
Summary: Use the rubberband resurrection method and disable the hibernation function on the SP3.