The account could not be used to sign in because you have exceeded the maximum number of allowed sessions

Error Message

When attempting to log in to ArcGIS Pro with an ArcGIS Online account, the following error message is returned:

Error:   
The account could not be used to sign in because you have exceeded the maximum number of allowed sessions.

Cause

The ArcGIS Online account has been used to log in to ArcGIS Pro on three different machines at the same time, and the maximum number of allowed active ArcGIS Pro sessions is three.

Solution or Workaround

Use one of the following options to resolve this issue.

Ensure the ArcGIS Online account is not used on more than three machines at the same time

• Close or log out of ArcGIS Pro on one of the machines.
• Organization members must request an administrator or member with privileges to manage licenses to end one of the active ArcGIS Pro sessions in ArcGIS Online. Refer to ArcGIS Pro: End a session for more information.

Note:
In some instances, administrators must unassign and reassign the member’s ArcGIS Pro add-on license. Refer to ArcGIS Pro: Assign or unassign an ArcGIS Pro add-on license or extension for more information.

Note:
If the methods described above fail, run the repair on ArcGIS Pro.

1. On the machine wherein ArcGIS Pro is installed, navigate to Control Panel > Programs > Programs and Features.
2. Browse to and right-click ArcGIS Pro. Select Change.
3. Click Yes when prompted, and click Repair > Next.

4. Click Install. Once the repair is complete, click Finish.