Hello Andrea,
The following links might answer your question:
https://scn.sap.com/thread/3287914
https://wiki.scn.sap.com/wiki/display/profile/Playing+around+with+SRM+7.0+webdynpro+screens
https://wiki.scn.sap.com/wiki/display/SRM/POWL+button+availability
Please review the information and let me know if you were able to resolve your issue.
Regards,
Gilberto Gallardo