My RPi B+ stopped booting suddenly after 1month working. I try 4 different usd cards and for all of them act (green) led flashes 4 time and no video and no power on usb ports and ethernet. I know it means start.elf not launched, but new NOOBS seems not having start.elf. I try formatted usd and act led is on permanently. Even I deleted bootcode.bin and act led is on permanently. So RPi seems have access to usd card and I don't know what the problem is. When usd is inserted clock pin of usd has no voltage (dc or ac). Can someone help me?
4 flashes: start.elf not launched
It probably means your NOOBS got a bad case of corruption. If you used the same file stored on your computer each time, download it from the RasPi website again.
Question: did you see the happy-rainbow-GPU screen?
First, I do not see any mention of the red light.
Second, no mention of voltage readings at the 5V and 3.3V pins.
At the very least we would need that much information in order to know whether the internal voltage regulator itself burned out.
4 flashes of green probably means the circuitry is actually working but that it cannot read the SD card. This can be due to too many insertions/removals.
Or, as mentioned in another answer the software on the card may be bad, or the card itself may have gone bad.