HiYasmin kazi,
1. Check whether user reached 312 profiles in USR04 table. if yes then remove some unwanted role to fix this issue.
2. Check the Role validity period for that user in which the missing authorization object is available
3,Run System trace to find out what exact authorization object is missing. whether it has been assigned to user. and check that role authorization tab color yellow or green.
Regards
Kiran.S