Sorry for the delayed response.
The page that the Force Password Change plugin redirects the user to is the standard "User Details" page of Joomla. We didn't create that page, and we don't modify the standard output. If the form is in a weird location, that's likely an indication of a template issue or an edit to the User Details page that is missing a div or something similar.
There really shouldn't be anything that the FPC plugin does other than a redirect when it detects the user is logging in for the first time. Can you check if other plugins may be conflicting with the FPC? Otherwise, please let us know your Joomla version, and we can try to investigate further. We haven't heard of this issue though, and FPC is used on *a lot* of sites.
Thanks,
Alex