This seems to be a recent change with version 4.2.0
I can confirm version 4.0.2 works with -ver 4. You can dowload it from the dssp v4 release page. You need a recent version of gcc to compile it (tested with gcc-11, but version from 8 up should work).
For information, gromacs 2023 has a built-in DSSP utility (gmx dssp) that is less cumbersome to build/use, and faster. You can find the release candidate here.