I Noted following problen on installation of piwik:
The problem is that not all visit are registered by piwik system.
I can assert it because separately I´m registering in parallel on server site the all Post request that are received on server, with the all related url and IP address.
And it is confirmed by Google analytics that is registering the same as my Server site.
i think that piwik 2.7.0 is NOT registering many mobile visits… though some are… case: i open my site with a chrome mobile (javascript and all that activated) and no visit is recorded, nothing… on the same page i request the desktop version and instantly piwik records the pageview…