If you are locked out of your FreeBSD instance and have lost access to the root account, you need to boot into single-user mode and reset the root password. These steps apply to FreeBSD 10.x, 11.x, and 12.x.
Access the instance console in the Vultr customer portal.
Click the Send CtrlAltDel button on the top right of the web console.
You can also click the Server Restart icon.
At the boot menu, press 2 for single-user mode. The prompt happens early in the boot process. If you miss the prompt, you need to restart the server from the control panel and try again.
mount -u -a -o rwto remount the disk RW.
passwdto change the root password.