In another thread, I discussed the problems that I was having trying to SSH-connect to my internet-hosted Raspberry Pi from my iPad Pro.
Now I suddenly found that I cannot ping the Pi either, from the iPad Pro, but I do get a response from the Pi when I ping the Pi from another machine.
What on earth can possibly be going on?
Later on I found that the problem had gone away. In the meantime, I had associated the iPad with a different SSID, and then - success! And then after that, going back to the original SSID, I found that it now still works. So weirder and weirder.