I am using a 2019 Macbook Pro 13" with Mac OS 10.15.3 (Catalina). I have a Dell D6000 USB-C dock and a Dell P2419HC USB-C monitor that can act as a USB-C hub. With both of these docks/hubs, I have the issue where I will plug in the USB-C cable to the Macbook Pro 13" and sometimes the USB devices or monitors will be recognized and sometimes they won't. Additionally, sometimes the Dell D6000 will provide power to the laptop and other times it won't.
Essentially, each time I plug the USB-C cable in to the laptop, it is completely random as to whether things will work or not, and this behavior occurs with both the monitor hub and the dock. If I unplug and replug the cable in multiple times, it will eventually work... sometimes on the first try, second try, or third try. Sometimes I will reconnect the cable 5-6 times before I get all external devices to be recognized PLUS power to the laptop.
I have reset the SMC and the NVRAM with no luck. I almost returned the D6000 dock until I realized the monitor was behaving the same way. I have a CalDigit Thunderbolt 2 Dock that I can plugin to the same laptop using a Thunderbolt 2 to Thunderbolt 3 adapter, and when using this approach, the USB devices show up every single time I disconnect and reconnect, leading me to believe that this could be a Dell hardware problem, or something about how the Dell devices work with Apple's hardware or OS. However the original post references an Anker device, and another post Deltaco, so it's tricky to know if this has something to do with Thunderbolt 3, or just with 3rd party vendors using USB-C.
So, my long-winded answer would be try disconnecting and reconnecting until everything works fine. Or try some other hardware or device to see what happens, I just don't have the disposable income to throw around testing this out.