JuiceSSH on Android not accepting IPv6 address

Using a current version of JuiceSSH on Android, I'm trying to set up a New Connection to my system at fe80::f9cd::4687::90cd::5da2. I've confirmed that I can ssh to that address from a Windows machine. But when I try to save the connection in JuiceSSH it tells me "Invalid Address". (I tried single colons too, no improvement. I haven't tried _no_ colons yet.) In case it matters, I'm using an Identity which has the same Private Key that I used from Windows, pasted into JuiceSSH as multiple lines between -----BEGIN OPENSSH PRIVATE KEY----- and -----END OPENSSH PRIVATE KEY----- lines, which seemed to be what JuiceSSH wanted to see (?). It's an ed25519 key, which JuiceSSH claims it supports; I'm not sure whether that's supposed to be indicated explicitly somewhere. But I wouldn't expect wrong key to cause an "Invalid Address" message. I presume I'm missing something obvious. Any ideas on what would be welcome. (BTW, I'm perfectly willing to try other Android SSH clients, but Juice seemed to be the most commonly recommended.)