We have found an issue with Huawei devices ( P10 Lite and P20 Lite 😞 Running the CySmart on Huawei devices don't show the BLE devices with Custom Services ( see the picture - samsung vs huawei ). Do you have any information about Huawei devices?
Since the other phones are able to see the BLE devices, I think its a Huawei specific issue. There are many websites reporting there is a bug in the phones. So, please check if they have fixed that bug.
