Why do you ask this question in a forum that is designed to point out useful information for folks. " USEFUL USER ARTICLE" Try beginner or general.
Did you search hotspot in the search window?
Did you search hotspot in youtube "Mikrotik hotspot"
Did you check out MT documents? https://help.mikrotik.com/docs/display/ROS/RouterOS
I know very little of hotspot but I do know there is a place to delineate how many MAC addresses can be assigned to a login or something like that.
Also ensure your pool is large enough for users and dont assign some users manually and some via pool to avoid overlap.
Probably in Profile settings...... Gluck.