Class not found

Thanks. I am using version 2 above. I still get Class 'ApiClient' not found.
I then checked psr4
return array(
'Symfony\\Polyfill\\Php72\\' => array($vendorDir . '/symfony/polyfill-php72'),
'Symfony\\Polyfill\\Mbstring\\' => array($vendorDir . '/symfony/polyfill-mbstring'),
'Symfony\\Polyfill\\Intl\\Idn\\' => array($vendorDir . '/symfony/polyfill-intl-idn'),
'Sendpulse\\RestApi\\' => array($vendorDir . '/sendpulse/rest-api/src'), <<< it is right here
'Psr\\Http\\Message\\' => array($vendorDir . '/psr/http-message/src'),
'Http\\Promise\\' => array($vendorDir . '/php-http/promise/src'),
'Http\\Client\\' => array($vendorDir . '/php-http/httplug/src'),
'Http\\Adapter\\Guzzle6\\' => array($vendorDir . '/php-http/guzzle6-adapter/src'),
'GuzzleHttp\\Psr7\\' => array($vendorDir . '/guzzlehttp/psr7/src'),
'GuzzleHttp\\Promise\\' => array($vendorDir . '/guzzlehttp/promises/src'),
'GuzzleHttp\\' => array($vendorDir . '/guzzlehttp/guzzle/src'),
);

I think the install was OK. I have done it at least 3 times. How can I check if the library is installed? Should I try reindexing or am I wasting my time?

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