As of Minecraft 1.17.x, the minimum Java version is 16 so anything lower will not work properly. The packmenu.mixins.json file has JAVA_8 compatibilityLevel and minVersion set to Java 8 when the minimum now is 16. This might be part of the reason my previous issue with the launcher is having troubles starting. Same is true for the mods.toml where it has dependencies.packmenu set for versionRange=5 - this should be updated to 7 for 1.17.x (at least for consistency). Thanks! -Steve - added more detail to a different issue. closing this one.