namespace issue

[Farshadi73]

I try to use SEOstats but get ClassNotFoundException

Attempted to load class "SEOstats" from namespace "SEOstats".
Did you forget a "use" statement for another namespace?

$seostats = new SEOstats();
or
$seostats = new \SEOstats\SEOstats();

I use PHP7.1 in Linux Ubuntu 17.4