Can’t remove rear cassette on hybrid bike

in Road general
I have a Shimano MF-TZ31 rear cassette and I need to replace the wheel bearing however I cannot get the cassette off. On my road bike it’s a simple task but my cassette removal tool don’t slip down to slot into the teeth. Am I missing something it does look like the cassette has a lock ring on it but I cannot find a tool or budge it myself. If you can have a look at the photos and advise please. 



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Park Tool FR1.2 should work