Without getting the spec manual that comes with each plc
A flashing power led usually means a dead shourt on the output 24VDC.
This is not a special signal - what is happening is either too much load or a dead short is across the + and -
The 24vdc supply automatically shuts down then restarts, sees the short again and shuts down causing the power led to flash.
I have had this before and the dead short was on for more than 8 hours with the unit powered up.
When I removed the wires from the 24V the plc sprang back into life like nothing was wrong. When I found the short (and it was a dead short) and repaired it all was well again .