Imposible to re-create new CalDav account on android and osx after cancelling /

Ciao to everybody, please newbie needing help here!
I have an account on instance.
I had it syncronized with Calendar (on my mac OsX 10.12) and DavDroid (on my fairphone 2).
I had just one calendar perfectely working, but… today I created a new calendar from nextcloud web page, and this one didn’t sync with Calendar e DavDroid, weird…
So I had the silly idea to eliminate and create my account again, but after cancelling now it’s impossible to recreate.

Now mac answers:

“Impossible to verify account or password”

And DavDroid is continuously loading:

“Wait, sending informations to server”

(I’m translating messages from italian).

Where is the problem?