Why is the WordPress Simple Fields plugin returning empty?

Question

WordPress

Not the first time I work with Simple Fields and everything has always been good, but this time they just refuse to work. Created fields, created a controller, connected to the page, filled in the fields (screen) - clip2net.com/s/3p7drAp
In general, everything is as always. On the page, in the right place, I make a selection:
<?php
$a = simple_fields_values("preimname, preimimage");
var_dump($a);
?>
And I get...nothing. I don't see any errors in syntax or anything else. Has anyone encountered a similar problem or have any idea about this? It is very important to resolve this situation as soon as possible.