The "UI missing....." message can be caused by 1 of several things. The most common is installing the original base game Engine 1 version of Combat Mission Battle for Normandy. That version will not run on Windows 10. There are 2 solutions. One solution (and least desirable) is to revert your computer to an earlier version of Windows. The most simple solution is to purchase one of the Engine Upgrades. If you already own any of the Upgrades continue installing through the Upgrade(s) and the message will clear.
If this is not the case and you are seeing this message with an Upgraded version of Battle for Normandy the next most common cause the program that is extracting/unzipping the download is corrupting the download. Try using a different program to extract the download. Bandizip is a great one that seems to work very well. Bandizip is a free third party program that we have no affiliation with.
Special note: Both the 3.0 and 4.0 Upgrades are all-in-one full game installers. You do not need to do the step by step installation.