Caller cannot hear us from one of our Yealink W59 phone, one way audio

Im having the same issues with the same phone. Were you able to find out why and how did you fix this? 

​@John Mapes 
I’ve had this issue in the past.

The setup was 1 base station with multiple handsets, each having their own account on the base.
1 account was registered with auto-provisioning. (worked fine)
3 accounts were registered with manual provisioning. (had one way audio)

How to fix:
in the web UI of the yealink go to Account > Advanced> at the top select account 2
Scroll down and look for RTP Encryption(SRTP) and set it to “Compulsory”
Scroll back to the top, select account 3 and do the same for all accounts that you have manually provisioned.

Why this fix worked:
This worked because the 3 accounts were set up with TLS as a transport protocol. 
If you used UDP then the issue must be something else. 
You can check the transport protocol in the web UI of the yealink under Account > Register > SIP Server 1 > Transport