Due to a problem in the Intel® Quartus® Programmer Standard Edition software version 18.1, Cypress* flash devices with density of 256 MB and 512 MB will fail to get programmed correctly. The Intel Quartus Programer may show succesful programming, but the flash would not actually be programmed.
To work around this problem, download and install patch 0.05 from the links below. You must install the Intel® Quartus® Prime Standard Edition software version 18.1 before installing this patch.
Download the version 18.1std patch 0.05std for Windows (.exe)
Download the version 18.1std patch 0.05std for Linux (.run)
Download the Readme for the Intel Quartus Prime Standard software version 18.1 patch 0.05std (.txt)
This problem is scheduled to be fixed in a future release of the Intel® Quartus® Prime Standard edition software.