If Dimensions crashes or loses connection with the server, then users who were active at the time will still be set as such in the database. The status can be cleared as follows:
Log into Dimensions as an administrative user such as 'sa'.
On the System tab, select User Records.
Locate and select the user and in the ribbon, click Inactive.
Please take note of the message regarding when to do this and click OK to continue.
Answer Yes to complete the process, No to cancel as required. The user will now be able to log back into Dimensions.
If you use Hosted Dimensions and do not have access to the correct login then please log a new case online and reference this article and include the name and if known the userid of the person affected.