I got the fix: change “System Locale” to English (United States) (and disable the UTF-8 beta option), reboot Windows. Not just changing display language and region. It is under Control Panel\Clock and Region\Region\Administrative on Windows 11.
Root cause: this is a compatibility bug of ElkRP2 with non-Unicode Windows system locales. ElkRP2 incorrectly reads its Access MDB security/database fields when the system locale other than en-US is used, even if the Windows display language and region are set to English / United States. As a result, a fresh database is falsely detected as password-protected, showing a masked password and locking the ID fields.