This can happen if you exceed your allotment of licenses. Note that, Teramind Cloud is licensed per user whereas Teramind On-Premise/Private Cloud are licensed per endpoint (computer).
Also, note that, The Hidden Agent will create a new employee account for each logged on user, which have to be licensed separately for the Cloud accounts. Similarly, if the same user logs in from different computers, you will need separate licenses for the On-Premise/Private Cloud deployments.
Check out the following articles to learn how to solve this issue:
License Overutilization Notification
Please note that while Teramind allows you to add more users/endpoints than your total number of licenses, you should be careful when overutilizing this feature. Adding users/computers beyond your license entitlements might cause unexpected results such as missing users/computers, login failures, possible incorrect data, etc.
To avoid this, you can turn on the license overutilization notification from the Settings > License Alerts screen.