Hi,
I see what the problem is then. Synonyms cannot be set for mutliple word keywords only single words. So “Playstation 4” will have no effect whatsoever, since it is composed from two separate words. I wonder why it allowed you entering multiple keywords into the synonyms input (I guess with copy/paste?), I will check that for a later release.
The most optimal solution would be for this to use the additional keywords inputs, however I guess you have a lot of records, so that could be problematic. Another possibility, is to use the custom code from this knowledge base.
You could use these keywords in the $replace variable like:
$replace = array(
'ps4' => 'playstation 4',
'ps2' => 'playstation 2',
'ps1, psone, ps' => 'playstation 1'
);