Hi,
I know you have answered this before but I get the same whenever I try to use the latest omnipay too.
I'm running PHP 5.5 on Ubuntu and I just get the cannot find 'Omnipay\Omnipay'. I've installed using composer and I've included the autoloader.
The autoloader generated looks like this -
<?php
// autoload_psr4.php @generated by Composer
$vendorDir = dirname(dirname(__FILE__));
$baseDir = dirname($vendorDir);
return array(
'Omnipay\\WorldPay\\' => array($vendorDir . '/omnipay/worldpay/src'),
'Omnipay\\TwoCheckout\\' => array($vendorDir . '/omnipay/2checkout/src'),
'Omnipay\\TargetPay\\' => array($vendorDir . '/omnipay/targetpay/src'),
'Omnipay\\Stripe\\' => array($vendorDir . '/omnipay/stripe/src'),
'Omnipay\\SecurePay\\' => array($vendorDir . '/omnipay/securepay/src'),
'Omnipay\\SagePay\\' => array($vendorDir . '/omnipay/sagepay/src'),
'Omnipay\\Pin\\' => array($vendorDir . '/omnipay/pin/src'),
'Omnipay\\PaymentExpress\\' => array($vendorDir . '/omnipay/paymentexpress/src'),
'Omnipay\\Payflow\\' => array($vendorDir . '/omnipay/payflow/src'),
'Omnipay\\PayPal\\' => array($vendorDir . '/omnipay/paypal/src'),
'Omnipay\\PayFast\\' => array($vendorDir . '/omnipay/payfast/src'),
'Omnipay\\Netaxept\\' => array($vendorDir . '/omnipay/netaxept/src'),
'Omnipay\\NetBanx\\' => array($vendorDir . '/omnipay/netbanx/src'),
'Omnipay\\MultiSafepay\\' => array($vendorDir . '/omnipay/multisafepay/src'),
'Omnipay\\Migs\\' => array($vendorDir . '/omnipay/migs/src'),
'Omnipay\\Manual\\' => array($vendorDir . '/omnipay/manual/src'),
'Omnipay\\GoCardless\\' => array($vendorDir . '/omnipay/gocardless/src'),
'Omnipay\\FirstData\\' => array($vendorDir . '/omnipay/firstdata/src'),
'Omnipay\\Eway\\' => array($vendorDir . '/omnipay/eway/src'),
'Omnipay\\Dummy\\' => array($vendorDir . '/omnipay/dummy/src'),
'Omnipay\\Coinbase\\' => array($vendorDir . '/omnipay/coinbase/src'),
'Omnipay\\CardSave\\' => array($vendorDir . '/omnipay/cardsave/src'),
'Omnipay\\Buckaroo\\' => array($vendorDir . '/omnipay/buckaroo/src'),
'Omnipay\\AuthorizeNet\\' => array($vendorDir . '/omnipay/authorizenet/src'),
);