Your Ooma Telo may be in the HD1 mode already. To make sure do the following:
Dial *#*#302 which changes to the HD2 mode, the Ooma Telo will reboot. Then dial *#*#301 which will reboot again and change you back to the HD1 mode.
Then if the HD1 handset won't Register to the Ooma Telo, you may have to clear the previous registration data out of the HD1 handset. Procedure follows:
Procedure to reset the Ooma Telo HD1 handset.
First, if required, go to My Ooma https://www.ooma.com/app/support/ooma-t ... -functions
, to view the Ooma Telo Handset button functions and location picture.
1. Turn off the Handset by pressing and holding the (red colored) End Call button, until the Handset goes off.
2. Press and hold the following two keys until told to release them later in this procedure:
Left Softkey and 0 (zero) key.
3. Turn on the Handset by pressing the (red colored) End Call button.
4. Release the two keys being held in step 2, Left Softkey and 0 (zero) key.
5. The Handset goes into auto registration mode.
Note: You will have to re-register the handset to the Ooma Telo.
Note: To all those users with the handset stuck in SEARCHING, when pressing the left Soft key + the 0 (zero) key, you must Continue to HOLD DOWN These Keys while turning handset back on.
Then and only then will the handset enter the registration mode, which then allows you to input the four digit code.
Register the Ooma Telo HD1 Handset:
Find the 4-digit PIN number for your Ooma Telo by logging into:
Bring the handset next to the Ooma Telo.
Set the Ooma Telo in registration mode by pressing and holding the Paging Key located on the upper right hand face of the Ooma Telo for 3 seconds. The Paging Key will start flashing rapidly.
When prompted on the handset, enter the PIN number found above and press the OK soft key.
When the handset successfully registers, a home screen will be displayed.