2018 versions of YHS33 not working with Shoretel/Mitel IP phones anymore?

[kndy]

Since 2016, employees (not front desk operators) have been using Yealink headsets YHS33 which worked with Shoretel/Mitel phones.

This month, a new order were made for several Yealink YHS33 and they are 2018 versions (although purchased in April 2019) and are not working. User can hear the person on the other end through the headset speaker but when they speaking into the mic, no one on the other end can hear.

We did testing on numerous phones, also on phones for employees who have the 2016 version of the YHS33.

Tested phones: IP480, IP485G, IP265 and IP230

Settings were checked on phones (wired, mic levels, did the headset, speakerphone test).

And 2018 version (purchased on April 2019) of the headsets purchased (a total of five) are not working. But yet the older YHS33 2016 versions that we have purchased years ago are working.