Sometimes, Oracle supersedes older OPatch versions. If 13.9.4.2.5 is no longer listed, the latest version (e.g., 13.9.4.2.6 or 14.x) will be backward compatible. Always check the readme of the patch you intend to apply—it will tell you the minimum OPatch version required.
OPatch 13.9.x requires a specific JDK version within the Oracle Home. If you see Java-related errors, verify your $PATH points to the correct java executable. opatch version 13.9.4.2.5 download