Hi, 

Make Sure you upload the diagnostic buffer, we need to see what is in there.

See the following article about how to get to the buffer:

Which information is entered in the diagnostic buffer of the SIMATIC S7 CPU with STEP 7 V5.x?

As your CPU seem to be in Stop, you may need to look at:

https://support.industry.siemens.com/cs/ww/en/view/11499205

Hi, 

It does not indicate any obvious reason. STOP due to IO error message suggest for me the CPU can not access the backplane. 

Check again the obvious things too(Memory Card inserted properly and it is damaged, CPU is not damaged in any ways)

Try to look for loose connection in the backplane. I have seen similar issues with these rack type. There is a similar post regarding to a different HW but the conclusion I believe applies to you:

S7 CPU416-3 PLC 'STOP due to IO Error' fault