Help with Flash memory reading

I see several points why your code doesn't work as expected.

As a very general point, you can't write data to a flash memory by simply activating WE. Consult the flash datasheet at the DE2-70 system cd, you'll see that it's a rather complex action to write data to a flash. Basically it can be done in HDL code, but not in a few lines of code.

As a more simple point, you're apparently using the flash control signals inverted. They are active low, shown by a# suffix in datasheet, but you set OE=1 and WE=0 and expect data at the data bus.

I wonder if DE2-70 has suitable examples to evaluate such basic operations, but I'm not very familiar to the Terasic hardware or software.