Error 500 on Order View and Invoices

[PurpleMan]

I'm Getting a 500 error when I try to view orders on the back end, customer front end and when I click sales>operations>invoices and it gives the following error:

PHP Fatal error: Interface 'Magento\\Sales\\Api\\Data\\InvoiceInterface' not found in {magento-root}/vendor/magento/module-sales/Model/Order/Invoice.php on line 24, referer: {webaddress}/admin/admin/system_config/edit/section/dev/key/6d2219cd23785e1829eee12dacc666cb79ad0b4f1fef7097ab3ca18ad5f6d540/

I've checked /vendor/magento/module-sales/Api/Data/OrderInterface.php and the file exists so I'm not sure what's going wrong.

[PurpleMan · Accepted solution]

Solved the issue, if anyone needs to know the answer was on this post here:

http://magento.stackexchange.com/questions/104564/magento2-interface-error

I reset Apache and everything started working fine