VHDL FILE_OPEN does not return correct status in Quartus

The problem here is that Quartus does not support memory initialisation from a text file in VHDL. I raised an enhancement request for this about 8 years ago, because Xilinx XST always has allowed the use of textio to initialise a ram. Annoyingly, Quartus does support this in verilog.

Just a NOTE: if it did support it - then you are doing it in the wrong way anway - it needs to be done via a function at initialisation time, not runtime in a process.

If the initialisation is easily done via a function, then Quartus does support initialisation via a function (unless it involves textio)

Otherwise your only option is to create a .mif file.