If someone already assigned the device to your TeamViewer account: Click Extras –> Options –> Security –> under Unattended access, activate the checkbox Grant easy access –> click OK. For more on how to enable two-factor authentication at the account level, check out our TeamViewer Community article.
Securing your TeamViewer account with two-factor authentication significantly reduces the chances of someone other than you is accessing your device(s). This approach is more secure than those involving passwords due to one powerful feature: two-factor authentication. The only way someone else could access that device is with the device ID and password, so if you’ve eliminated passwords, you have limited access to only your device (and your group, if you have assigned the device to a group). You simply need to be logged in to your account. When Easy Access is enabled on a device and that device is assigned to your TeamViewer account, no random or personal password is required.
The newest secure way to access a device with TeamViewer is through Easy Access.