Ensure your MT4 terminal is version build 224 . If your broker updated to build 1353+, the decompiler will fail. You would need an old terminal installer (often unavailable from official sources).
However, the solution is fraught with peril. The "repack" ecosystem is a minefield of malware, legal violations, and broken promises. While build 224 is the most compatible for decompilation, using a cracked tool often puts your trading capital (via infected terminals) and your legal standing at risk. ex4 to mq4 v4 0 224 1 decompiler repack
If you must decompile a build 224 file, purchase the official decompiler from a reputable source (if it still supports that legacy build). If you cannot afford it, consider the EA lost. The cost of a hacked PC or a copyright lawsuit far exceeds the price of a new EA. Ensure your MT4 terminal is version build 224