Maximum User Limit Issue
The amount of System Users you subscribe for determines the length of your Geer ERP subscription. Once you've reached that number, the system won't let you add any more users. For illustration, let's say you subscribed for 10 users. You will receive the warning below if you have already established 10 System Users in your account and attempt to create an additional 11.

To fix this, you will either have to:
1) Buy new users or
2) Disable the current users
However, occasionally you might continue to experience this problem even though the number of System Users allowed by your membership plan has not yet been reached. For instance, you have only established three users while having a maximum of 5 System Users. But you receive the aforementioned notification when adding a fourth user. This may be due to the fact that for some usage, the "Simultaneous Sessions" field has a value larger than 1.
Each concurrent session counts as one system user. For instance, if you created three users and one of them has "Simultaneous Session" set to three, then you have a total of five users, or five simultaneous sessions/system users, as three plus one plus one is five.
You will need to limit these users' concurrent sessions if you want the system to let you create more users. To do this, go to the User's profile and adjust the "Simultaneous Session" setting as necessary under Security Settings.

Note that there is no restriction on the number of Website Users you can establish.