Hi @unkown_25
When a user accesses a site collection the first time, they are added to the profile. Howevere, a property named tp_IsActive in the USER INFORMATION LIST is set to false until the user interacts with the site by adding a document or clicking a link. When this property is false the user information will not be synced by the jobs WSSProfileSynch and WSSSweepSynch .
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.