Within Teamwork, you can reset a user's password by resending their invitation to your site.
Click the More option from the main navigation and select People from the dropdown menu.
In the people area, select the People tab from the horizontal menu.
In the top right of the People list, click the options button (three dots) and select Send Invites from the dropdown menu.
In the Send Invites modal, go to the Resend Invites tab where you can choose from the list or search for the user's name. You can also filter to a specific company's users.
Check the box to the left the user's name and click Send Invite Email Now.
Once the invite has been sent, the user will receive a link where they can set/reset the password they wish to use for accessing their your Teamwork site.
Note: By default all users are required to create a strong password. This must consist of at least 8 characters in length and include one letter and two numbers.
For more information, see: Changing Your Password