Only the newer iStream 3 is still available on the Roberts website. The 3L is no longer available and has older WiFi and Bluetooth standards because of the older hardware.
I can't say for sure whether this plays any role, as the specifications are not specified more precisely or are only available behind a paywall (sic!!!). But it is possible that certain Bluetooth functions of modern devices are not supported, for example new high fidelity transmissions for which BT 5.x is necessary. WiFi doesn't matter, as the new routers also support older standards and audio really doesn't take up any bandwidth.