This description is only valid for Windows Embedded Standard 7., not for Windows 10 IoT. With Windows 10 IoT, Microsoft Multitouch is supported.
A touchscreen device is recognized by IGEL Universal Desktop W7, or a driver from a touchscreen manufacturer has been installed, but the touchscreen does not work, or does only work with a pen but not with multitouch more than one finger.
Microsoft Windows Embedded Standard 7 (WS7E) which does not include Microsoft Multitouch - this is excluded by license and cannot be installed later on. All touchscreen devices with drivers that need this component will not work. Only drivers that do not use Microsoft Multitouch features can provide touch functionality.
A reference of WS7E features is available at http://blogs.directinsight.co.uk/ws7p-vs-ws7e-flavours-of-standard-7/ .
For a specific touchscreen device there is no solution. But when choosing a device please note Microsoft Multitouch is not available in IGEL UD W7 and evaluate a sample device to test the touch function.