If your Mac came out after 10.6.3 (roughly mid-2010), the standard retail disk may not boot. You might need the specific "grey" restore disk that originally came with that machine.
Connect your 8GB or larger flash drive to the Mac. download snow leopard 1068 dmg google drive upd
This is the most common issue when installing vintage Mac operating systems. It happens because the security certificate embedded in the installer expired years ago. If your Mac came out after 10
You can find a Snow Leopard 10.6.8 DMG mirror hosted on Google Drive for high-speed access. download snow leopard 1068 dmg google drive upd