403 ServiceError: unknown when Bot tries to get conversations in a team

When my Bot requests GET https://smba.trafficmanager.net/emea/v3/teams/19:[id]  it gets a response with the expected data.

But for GET https://smba.trafficmanager.net/emea/v3/teams/19:[id]/conversations it gets a 403 and

{
	"error": {
		"code": "ServiceError",
		"message": "Unknown"
	}
}

what could be causing this?