AVR 5000 switch backs into stand-by / turns off

Hi, Try this. Hope this helps and I have the link here to the manual.
Processor Reset
If the AVr behaves erratically after a power surge, first turn off the front-panel
main
power switch and unplug the Ac power cord for at least 3 minutes. plug the cord back
in and turn the AVr on. If this procedure doesn't help, reset the AVr's processor as
described below.
note: resetting the processor will erase all user configurations, including speaker and
level settings, and tuner presets. After a reset, reenter all of these settings from your
notes in the Appendix worksheets.

To reset the AVR's processor:
1. press the front-panel Standby/on switch to place the unit in the Standby mode (the
Standby Indicator led will turn amber).
2. press and hold the front-panel Standby and memory/folder buttons until the reSet
message appears on the front-panel message display.
3. press the memory/folder button again to reset the AVr's processor.
If the AVr does not function correctly after a processor reset, contact an authorized
harman
kardon service center for assistance.
to locate an authorized service center,
visit our web site at www.harmankardon.com.

https://www.harmanaudio.com/on/demandware.static/-/Sites-masterCatalog_Harman/default/dw409ee4c9/pdfs/AVR700NEW_OM_EN.pdf

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/laura_08254539050d64db

Turn your vollume right down,Then try it again,If it doesn,t work then, It was over heated end fried something inside of it.

Your power switch is going bad. Start shopping for one now, because it's going to fail completely on future. Common problem.

Open the unit and measure the voltage across the reset microswitch on the transformer board (with the unit in standby). It should be a hi signal, over 3 volts. If it is low, below 1 volt (when you can't turn it on) it is sending a constant reset signal to the cpu. Remove the switch and try again. If the problem goes away, the switch was bad. Its a service switch so you don't have to replace it.

Disconnect all speakers at the receiver and turn it back on, if it stays on post a comment and I will help you troubleshoot further. If it still cuts out, it needs to go to service for repair. Hope this helps.

Make sure it is not in download mode!! a little switch on the back of the device

Hi, this is an issue with a sensor on the power module. To fix it you must replace that part.

You're drawing too much power from it. Sounds like maybe your sub is hooked up wrong, double check that.

By now the folks who asked this have certainly solved their problem, but in case anyone else has this same question:
If the color change from red to green on the Power button indicator light and stays that way, the receiver is most likely working fine, it's just that your front-panel display is OFF.
1. Check the DIMMER mode by pusing the buttom on the front panel -- it may be set to OFF.
2. Push the PURE DIRECT button on the front panel (or remote control) -- it may be ON, which turns off almost all of the front-panel display. (Alternately, change the AV source, which turns Pure Direct OFF.)
HOWEVER if the power light flashes rapidly, the amp's overload protection circuit may have been triggered by a feedback loop or other problem, such as a shorted or bad cable connection. Turn off the power and unplug the receiver. Look for problems starting with shorted speaker wires or cables. Then make sure the receiver's not still hot (wait 5-10 minutes to let it cool), and remove obstructions or anything blocking the top vents. Plug it back in and power up again. Immediately change the Source selector to something unconnected, and turn the Volume DOWN just in case there's a feedback loop (hum/squeal/noise that can overload things and cause the protection circuit to trip again). If you can see the display, go to a low level (around -50dB should be fine) before the delayed speaker amp output clicks on. Then carefully switch back to the problem source -- if that's the problem, switch off again immediately and re-check all of the cable connections at both ends, the receiver and the source component, and make sure you don't have a feedback loop due to a recording device feeding back a signal. All VCRs and CD/DVD-recorders should be hooked up to the VCR, DVR or TAPE/CD-R "IN/OUT" jacks with IN being connected to the cables marked OUT on the deck and vice versa. (That confuses even us experienced guys sometimes!) Also, no MONITOR video or audio outputs should be connected to the recording decks, nor should the TV outputs be fed back to the recorders. The same goes for the digital IN/OUT jacks for CD recorders; use only the same number IN as OUT for each component (Optical IN/OUT #4 and #5 are the two digital IN/OUT pairs on the AVR-3803).

The flashing light is not a stand by...that a service light telling you it has a problem that needs to be fixed...