I tried to simulate it but I wasn't able to do it. Is your file in any synchronized folder (One drive, Gogle drive)? Isn't your file R/O? Does PSpad show any meessage?
Ctrl+S does save your file or not? -- <https://forum.pspad.com/read.php?4,73798,73802> PSPad freeware editor https://www.pspad.com