ATtiny85 dev board keeps rebooting, cannot program

Dear All,

I have an ATtiny85 which worked well, however after a power cycle the onboard LED keeps flashing.
I looks like the board is constantly restarting and I cannot re-program it.

I've tried/checked:
5V is present
Cable workes OK with other ATtiny85's

Any ideas on how I can fix this bricked board?

i am a little inexperienced but i wanted to ask a few questions (possibly i could answer after that)-

  1. did you have the wdton fuse programmed? check in the boards.txt file. if yes , then how many seconds the watchdog waits before generating an interrupt/reset?
    2)does the led have a current limiting resistor(mostly this would not cause that.. just asking)
  2. do you have a high voltage serial programmer?
    4)if not , what are you programming it with?
  3. what does the last uploaded sketch tell it to do?
    6)is the power supply stable enough? i mean can it handle the load of what it is powering?
    (note- this is my first attempt to answer , sorry if i said anything wrong.)

Thanks for your message!
Please find the answers below:

The watchdog is not programmed.
The LED is an onboard LED, I guess there is a resistor.
The board is programmed with de USB interface on the board, see picture please.

The last program was a very simple delay output based on input.
The power supply is 500 mA.

Please note that I use several identical boards and they all work good.
Only one is giving problems after a powercycle.

i am a newbie but i suggest you (if you have any arduino or if you have any programmer) to use serial programming (if you don't have the rstdsbl fuse programmed) if you have a high voltage serial programmer then the rstdsbl doesnt come in between ( as far as i know) because in both of these methods, the upload would be done and you could burn the bootloader for this board again (please tell if you have any arduino or any development board which can work as an isp. and also if you are using the arduino ide) thanks!

Thanks for your help!
I can confirm I use the Arduino IDE and that I have an USB to TTL programer,
I will check how to program this way and I will try if that works.
Please give me a couple of days.

be sure to temporarily remove any sensitive parts before doing anything if you are using high voltage