looks like your PI and ECC have SLD registation issue.
Please make sure both SAP systems (ECC and PI) connected to same SLD.
Transaction codes you need to check as below in both systems
- RZ70
- SLDAPICUST
- SLDCHECK
Once all TCodes are checked...
Restart SAP PI systme - This will clear PI system cache
Please tray again...
If this is still not working let me know
Note: Its better to use SLD in PI (Local SLD)
-Yogesh