EGX - Special G/L indicator not defined or incorrect

Dear Exparts

We are facing issue during configuration of Vendor retention process.

1) Activate business function LOG_MMFI_P2P

2) T Code OMR4 new document type for vendor retention entry (RT)

3) Special GL creation FBKP (H)

4) Define control parameter for retention T Code OLMR (H)

5) Define transaction key EGX

6) OBYC - Special GL input in the EGX

Now error is coming Special G/L indicator  not defined or incorrect

Is their any other configuration left?

Regards

Tarek