If you are receiving the Trial dialog in your application when you deploy it to a client PC then your solution is likely missing the license data. To resolve this issue:
Load your project and in the Visual Solution explorer and select the Show All Files icon. In your solution you should then see a file called licenses.licx, double click on the file to open it and you should see the a line which says:
DTI.ImageMan.Twain.TwainControl, DTI.ImageMan.Twain, Version=x.0.0.0, Culture=neutral, PublicKeyToken=3ff15c974c5defd8
If you do not see this line or do not see the file then you must add the ImageMan.Net Twain controls to the toolbox and then drag an instance to a form in your application. Then you can delete the control from the form. If you look in licenses.licx you should see the line listed above.
You must then rebuild the solution to get the license data compiled into the application.
Also check to confirm that the ImageMan developer license is on the machine on which you are doing the build. The file is located in the CommonProgramData \dti\licenses dir and is called: ImageManNetTwani.lic.On Windows Vista/7/8 this will be the c:\programdata\dti\licenses directory.
If the license file isn't in that location you must reinstall the ImageMan.Net Twain install which you can download from the My Products page at http://www.data-tech.com/myproducts/login.aspx.
Also if you are using ImageMan.Net Twain in an assembly thats being loaded by another exe you must add the license info to the exe solution using the steps above as the license key is loaded from the exe not the assy thats using the control.