First check that you are not logged in to Dimensions on another computer — this error can be a genuine warning. If you are sure you are not logged in elsewhere, the error has occurred because Dimensions was not closed properly — for example, after a power cut or the machine being closed while still logged in. To resolve it, an administrator needs to mark your session as inactive. They will need access to the System Control and User Records areas — typically via the hosting.admin user or a CLOUD\ account with admin permissions:
In Dimensions, click System, then click User Records.
Click the relevant user in the list.
Click Inactive.
Click OK on the first warning message.
Click Yes on the second warning message.
You can now log in as normal.
You can also enable Master Status for a user, which allows them to log in even if there are connection issues:
Click System in the main menu.
Click User Records.
Find the user and click Options.
Click Edit.
Tick the Master Status checkbox.
Click Save.