Can you please provide a user guide for T42S?
User Guide for T42S
Here are few links that may help you:
https://netstorage.ringcentral.com/guides/rcyealink_t38g.pdf
https://netstorage.ringcentral.com/datasheets/phones/yealink/t42s.pdf
https://www.ringcentral.com/office/voip-phone/yealink-t42s.html
As per this link it i suggested to contact Tech Support Team so that they can help get you if you face any issue:
https://community.ringcentral.com/questions/28150/t42s.html
Hope these help
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