If there’s an issue with not enough space in the system partition still, you might also try deleting the built in EsFileManager.apk under /system/preinstall in TWRP. There is a wipe cache button that shows up immediately after flashing a zip. You want to execute that wipe and/or go to Wipe tab, hit advanced wipe, check dalvik cache and cache boxes, swipe to wipe. Then go to advanced tab, fix permissions, do not check fix SE Linux contents box, just swipe to wipe, then hit reboot. Sorry for sounding like a broken record with these steps. It’s a fickle thing and unless you have paid for an advanced Fidelizer ROM there’s negligible use for it in the end. If you have the free time to try stock 1.2.4 and it works? Then it was a case of a wonky state of affairs with your player and its rom. If it doesn’t work there either, then there’s something wrong with the process you’re going through.