Ok... my bad. Found the correct URL for my NextCloud calendars and it works like a charm
Now I'll dig for the GoogleCalendar link.
Thanks for your support.
Case closed for me.

...

First double check your calendar URL: Does it give a valid ICS file as response?
If you open 'MY_CALENDAR_URL' in a browser, you can save the output. It should look like:

BEGIN:VCALENDAR
PRODID:-//Google Inc//Google Calendar 70.9054//EN
...


Indeed, it doesn't return an ICS file.

when I ...

I have the maxitems defined.
var calendars = {}
calendars.perso = {
maxitems: 5,
url: 'https://calendar.google.com/calendar/',
icalurl: 'https://calendar.google.com/calendar?cid=...'
}

...

columns[5] = {
blocks: [calendars.perso],
width: 4
}

...

screens['tablet'][3] = {}
screens['tablet ...

Just saw the previous answer.
Update to last version (thanks to git)
Modify the index.php file (set debug variable to 1)
--> Good news is that I don't have the 'loading...' displayed, bad news is that it doesn't show anything at all.

When trying to access through the ./vendor ... I now have
RAW ...

Hello,
I have a similar problem. Calendar is not loading. Can't tell for preivous version as it is my first installation of Dashticz (which is fantastic by the way!).

When I tried the
"./vendor/dashticz/ical/?time=1585600958180&maxitems=6&url=MY_CALENDAR_URL", I got the following
JSON ...