Hola Jose
Recuerda que desde la ver 2.7, los logs han sido mejorados y ahora son registrados en una tabla nueva
{logstore_standard_log}
De manera que posiblemente, es por eso que no está obteniendo datos de la anterior {log}, para ello el propio plugin te ofrece la alternativa
Note for Moodle 2.7
Moodle 2.7 changed its internal logging system, so you need to enable "legacy login" to do this plugin compatible.
Go to Plugins -> Logging -> Manage log stores and ensure that "Legacy log" its enabled.
This change will enable logging only after enabling it, so if your course already started, course dedication calculations won't be accurate.
Alternatively you can download new 2.7 / 2.8 beta version from this link. This version uses new Moodle logging system and doesn't need to enable legacy logging, but hasn't been tested properly.
Espero que pueda serte útil.
Saludos!!