CIsco CP-8851 unable to do blind/direct transfer with Zoom Phones

[new-user3240543]

My organization recently migrated to Zoom Phones from RingCentral for our VOIP provider. Previously, the CP-8851 phone could transfer calls by following this process:

1. A customer calls the phone number
2. The employee answers the call
3. The employee presses “Transfer” 
4. The employee enters and calls the phone number to transfer
5. The employee presses “Transfer” again before the call answers (to do a blind transfer)
6. The phone calls is transferred to the other phone number 

However, now on step 5, the call disconnects abruptly. All the other functions work fine such as the sidecar/KEM, warm transfers, and speed dials. Even though I believe it to be a Zoom issue, Zoom support says this is a Cisco IP phone issue. 

This video also demonstrates the procedure that should be working. However, the call disconnects after the destination number is entered and the “Transfer” button is pressed for the second time.

Has anyone experienced this issue and/or know how to resolve it?