Maybe your file is too big. There is limit for automatic highlight. Open program settings / Direct edit Find line HLUpToSize and change value e.g. to 500000
You can anytime activate code highlight manually by toolbar button or in the menu View / Syntax On the statusbar should be highlighter name, if highlighter is recognized by file extension -- <https://forum.pspad.com/read.php?2,71783,71784> PSPad freeware editor https://www.pspad.com
