Insert the mute button into the knob assembly. It can only go in two ways. Ensure the speaker portion of the mute icon is on the same side of the assembly as the FFC connector on the PCB.

While ensuring the mute button doesn't fall back out, insert the knob assembly into the knob assembly carrier. It will only fit one way due to the FFC connector.

While ensuring the mute button doesn't fall out, insert and tighten the two JIS-000 screws.

Carefully align the knob carrier assembly over the four guide pins and gently press the knob carrier into place. Be especially careful with the two smaller guide pins.