Are those small sparklines working anywhere else in your piwik?
Does the system check of Piwik show any warnings?

System check is successful.
Only on this place i can not see the sparkline. Other charts works well.

If you "open the image in a new tab", do you see an error page?

On open the image it comes a redirect to Dashboard. The nginx error log said nothing.

On the place Location / Continent it work on my site!

Demo:
https://demo.piwik.org/index.php?module=CoreHome&action=index&idSite=7&period=day&date=yesterday#/module=UserCountry&action=index&idSite=7&period=day&date=yesterday

It was a wrong nginx config:

 59         location / {
 60                  try_files $uri /index.php;
 61         }