I've found this on apache2 error.log:
PHP Fatal error: Maximum execution time of 30 seconds exceeded in piwik/libs/jsmin/jsmin.php on line 136, referer: piwik/index.php?module=CoreHome&action=index&idSite=1&period=day&date=yesterday
Also, when I removed all piwik files and uploaded again, Piwik showed an error which states that the size of some language files were not the expected and I had to upload them as binary files.
PHP Fatal error: Maximum execution time of 30 seconds exceeded in piwik/libs/jsmin/jsmin.php on line 136, referer: piwik/index.php?module=CoreHome&action=index&idSite=1&period=day&date=yesterday
Also, when I removed all piwik files and uploaded again, Piwik showed an error which states that the size of some language files were not the expected and I had to upload them as binary files.