Hi Emir,
Actually after the init its may take time reach RSA7.
Once your delta was enabled then please observe at source system Tx - RSA7, once you see the increasing record count(against your data source) from 0; later you can run delta info pack.
Please wait certain time and later you can trigger your delta info pack.
Mean while run this program SE38 - RSC1_DIAGNOSIS and check it whether delta records pulled or not.
Thanks