The ANO Rotary Navigation Encoder breakout has 9 pins. Here are the details.

• ENCA - This is the rotary encoder A pin.
• ENCB - This is the rotary encoder B pin.
• SW1 - This pin is the center button.
• SW2 - This pin is the down button.
• SW3 - This pin is the right button.
• SW4 - This pin is the up button.
• SW5 - This pin is the left button.
• COMA - Common pin A for SW1, ENCA, and ENCB. Set to ground or VCC - usually ground - so that you can use the microcontroller internal pull-ups for the button/encoders. You can also use a GPIO pin and pull it low.
• COMB - Common pin B for SW2, SW3, SW4, SW5. Set to ground or VCC - usually ground - so that you can use the microcontroller internal pull-ups for the button/encoders. You can also use a GPIO pin and pull it low.

COMA vs COMB

There are two separate common pins: COMA and COMB. These are "common" to two different sets of pins (see above). The Adafruit Rotary Navigation Encoder Breakout does not tie the two common pins together. So be careful when wiring things up to not miss or incorrectly wire COMA or COMB with respect to the other pins.

The diagram from the info sheet shows this more clearly. The missing connection for CH.B to COM.A is probably a mistake.