It is possible that toothpaste residues or lime have accumulated underneath the metal ring above the gray rubber gasket. For this reason, the ring may behave somewhat stubbornly during removal.

Insert one arm of a pair of tweezers or a small flathead screwdriver underneath the bottom edge of the metal ring sitting above the grey rubber gasket.

Use your tool to carefully pry up the metal ring.

The metal ring is held in place by small plastic clips. During reassembly make sure, it snaps back into place.

When prying up the metal ring be careful not to puncture or tear the grey rubber gasket.