How to access On Chip Memory in VHDL

Apparently you made a modification to your post that triggered the forum's antispam system. I've approved your post and it should now appear.

As for your problem I don't see anything wrong at first glance, except that you don't generate or use any reset signal, which is bad practise. Still it doesn't' explain your symptoms.

Can you have a look at all the warnings written by the Quartus synthesizer when you compile? Especially messages about your .hex file being not found or in a bad format. Those usually generate only warnings and not errors.