License is not displayed error in WIXUI_Minimal.

From here

There is a known issue with the rich text control used to display the text of the license file that can cause the text to appear blank until the user scrolls down in the control. This is typically caused by complex RTF content (such as the RTF generated when saving an RTF file in Microsoft Word). If you run into this behavior in your setup UI, one of the following workarounds will fix it in most cases:

• Open your RTF file in WordPad and save it from there in order to remove the complex RTF content from the file. After saving it, rebuild your MSI.
• Use a dialog set other than the WixUI_Minimal set. This problem typically only occurs when the license agreement screen is the first one displayed during setup, which only happens with the WixUI_Minimal dialog set.