Find the subject that is costing you the test
Failing by two questions rarely means you know nothing. It usually means one subject is quietly eating your margin while the rest look fine. This reads what your own practice runs saved on this device and tells you which one it is.
Reading what this browser has saved.
What it is reading
Two things, both already on this device. The first is your review deck: every question you have answered wrong is kept, comes back on a widening schedule, and leaves the deck after three correct answers in a row. The second is a running count of how many questions you have been asked in each subject and how many you got right.
Both matter, because on their own each one misleads. A pile of road sign cards looks alarming until you notice how many sign questions you have answered in total, and a subject you have barely been asked about tells you nothing at all. That is why a subject is never named as your weak spot until it has been asked enough times to mean something, and why the page shows the raw counts next to every bar.
Why the fix is a different test, not more of the same
The instinct after a failed run is to take the same practice test again. That mostly re-tests what you already know, because a mixed test asks a few questions from every subject and the ones you are good at crowd out the ones you are not. If right of way is your gap, a mixed test of twenty will hand you a handful of them and call it practice.
So the tool links straight into a run made entirely of the subject you are weakest at. A whole run of nothing but right of way is unpleasant, and it is also the fastest thing you can do with an hour. When that subject stops being the lowest one here, come back and the tool will point at whichever one took its place.
Nothing here leaves your browser
There is no account on this site, so there is nowhere for your answers to go. The deck and the subject counts are written by your browser while you practise and read back by this page. They are not sent anywhere, they do not follow you to a phone, and clearing your browser data deletes them for good. The button at the bottom of the tool does the same thing deliberately, for one state at a time.
If the tool says there is nothing saved, that is the honest answer rather than a bug. Take a practice test and come back: one run is enough for it to start telling you something.