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Enable “Ignore the end call event from the headset“ in the Ringotel desktop app Settings (Menu → Settings → General tab). With this option disabled, the Ringotel app will disregard the received end call HID commands from the headset. This helps to prevent situations where an incoming call on Teams terminates an active call on Ringotel.
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Additional notes
Ringotel call gets disconnected the moment the screen share session in Teams is started. Same thing happens with a conference call when a screen share is started. The issue is observed in Teams Classic version.
Solution
Please advise users to update to Teams 2.0 which doesn't have the above mentioned issues.