I cannot tell you the reason why the order was canceled. There could be a lot of reasons
payment processor sent a message back for canceling the order
someone actually canceled it from admin
But I can tell you how to make it invoice-able again.
Take the order id. The entity_id field in the sales_order table, not the increment id.
Let's say it's 110.
The data you are looking for 'QTY' on Checkout page. That comes by knockoutJS in Magento 2. Knockout basically bind data to HTML template and serves dynamic content.
If you can check "Application" Tab (F12), In Local Storage > Mage-Cache-Storage > Cart (Section Data) driven from Knockout. You can see QTY, Options and all other parameters there.
I got solution for this issue.
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../lib/internal/Magento/Framework/ObjectManager/etc/config.xsd">
<preference for="Magento\Sales\Model\OrderRepository" type="Vendor\Module\Model\...