Years ago, MetaQuotes (the developer of MetaTrader) updated the MT4 compiler to match the stricter, more secure architecture of MetaTrader 5 (MT5). This update completely changed how .ex4 files are structured.
For older files, the tool generally operates through a simple interface: Ex4 To Mq4 Decompiler 5.0 1 Exe - Google Groups
Are you trying to or error in an old tool?
Декомпилятор: Декомпиляция ex4 в mq4 ? Конвертер mql - Expforex