Semi-secure calls are simply secure calls between the device and the FreeSWITCH (which is in the cloud), but from that point, it switches to the SIP trunk which is used to call the landline in a none secure call.
Lately, semi-secure calls are not working in many countries due to new regulations, in fact, more and more countries issue new regulations which block calls from SIP trunk to landlines. the reason is that it is being used for fraud and using fake numbers.
The fact it is working for some countries and not for others means that there is no issue with the Kaymera Software.
If your country doesn't have such regulation the reason that your device is not managing Semi secure calls is that probably the feature is not set up correctly.
To fix this issue, try to turn it on and off a couple of times and restart the device.