GSP 670 firmware update added new feature, you can now change the connection mode : r/sennheiser
Sennheiser on Twitter: "The new PXC550-II firmware (v 1.5.21) ensures compatibility with iOS 13.4. Please update your PXC550-II to the new firmware before you update your phone to iOS 13.4 and enjoy
Error message when trying to update Headset Firmware GSP 670 : r/sennheiser