Common error on sql_counter on Ver 2.1.5

Hi all, I recently installed freeradius Ver. 2.1.5 and I'm trying to configure it to work as a previous installation of Ver. 1.1.x. I'm stuck at sql counter module. On 1.1.x I use the common sessioncounter counter with sql module, but with 2.1.5 I got the message "rlm_sqlcounter: Could not find Check item value pair". I believe the configurations are indentical for both versions of freeradius, but I'm obviously missing something. Can someone help me to find where can be the error? I think it's a trivial one, but I'm stuck since 3 days. Thank You for interest. Mauro Iorio