MBP 13" 2010 blink a folder with "?"

Hello yesterday I turn on my MBP and it doesn´t load the system, instead it blinks a folder with "?".

A Few months ago, I´ve upgraded to a SanDisk SSD and 8GB Corsair Ram, it everything was perfect.

When this issue happens I changed the hard disk the my old (original one) that is working fine, and I reveiwed all connections, but the folder still blinking.

When I plugged a bootable pendrive, it runs the system but doen´t found any hard drive.

Anyone can help me? Thank you very much.

My System: MBP early 2010, Core 2 Duo, 8GB RAM, 256GB SSD, OSX Mavericks, Windows 8 BootCamp