Hello everyone. I have a problem whan I try to connect PLC s7 1200. I have a s7 1200 plc cpu1214C dc/dc/dc.

At last week , there is no problem. And I can connect to PLC and program it .in others words it work correctly.

But today, when I connect power 24VDC to it , the Error Led start to blinking (RUN led is green and ok ).

In TIA V17 , I can only see IP address of plc , and I can not assign New IP address. When I try to download program to It , the following error appear:

"connection failed. Selected online target is not reached....."

I will be grateful if anyone help me.

(I have Windows 10 , 64bit

Hi EhsanNiknami13701123

Have you configured the right Power Supply in TIA Portal? Error LED blinking may be due to mismatched hardware configuration (Status LEDs) 

Have you tried restarting the PLC and the power supply?

Is your PC's IP address in the same subnet as the PLC's IP address?

Have you temporarily disabled the firewall or antivirus to check if they are blocking the connection?

Hello EhsanNiknami13701123,