ET200S RS1e-x 3RK1903-0AL00 NOT READY Starter cannot be operated by host plc

Hello,

we have a siemens ET200S RS1e-x reverse starter:

card = 3RK1301-0BB10-1AA3

terminal = 3RK1903-0AL00

This reverse starter is already commissioned with IM151-8F PN/DP CPU.

System is working, though many times we get fails from RS1e-X. At the plc we see that the card does not report fault but it states NOT Ready. Looking at the manual page 133 (4-41) NOT Ready means that the starter cannot be operated by plc. (Profibus mapping of starter to plc)

Manual: https://support.industry.siemens.com/cs/ww/en/view/6008567 

I would like to know which are possible sources of error that causes reverse starter to be NOT ready for operation?

Thanks in advance for your support.

Best Regards,

Gonzalo