Connect to DBMaker 4.3 database from access 2013 - VBA code

In a vba module of Access 2013, I connect to a table of a DBMaker 4.3 database:

Dim Conn as New ADODB.Connection
Dim rstTT As New ADODB.Recordset

Conn.open "Provider=DMOLE43;User ID=myUserName;Password=myPassword;
Data Source=myDatabaseName;"

then I open a table like below:

rstTT.Open "select * from MyTable where MyField = 'C90000'", Conn

I'm sure that exists a record with MyField equal to 'C90000'. So, why is rstTT.EOF = true?

I tried to open the table like below:

rstTT.Open "select * from MyTable where MyField between 'C90000' and 'C90000'", Conn

and rstTT.EOF is equal to False (that's right).

Where is the problem?

Thanks to anyone who can help me