Simple: the ACE engine must be installed and registered on the machine.
If this is a different PC from that with Visual Studio installed, then install and register the appropriate version of ACE - if your app is built for 64 bit, you need 64 bit ACE, and if it's a 32 bit app, you need the 32 bit ACE engine registered.
If it's the same PC, then probably you are building it for the wrong target: 32 bit instead of 64 or vice versa. Check your IDE build properties to find out which version it builds for and include that in your command line parameters for your "manual" build.
But do yourself a favour, and don't do it like that! Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead.
When you concatenate strings, you cause problems because SQL receives commands like:
SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'
The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:
SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;
Which SQL sees as three separate commands:
SELECT * FROM MyTable WHERE StreetAddress = 'x';
A perfectly valid SELECT
DROP TABLE MyTable;
A perfectly valid "delete the table" command
And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.
So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?