This problem was mentioned in another thread, but there is no detailed information there.
If you look at the launcher logs, you will find attempts to load Chromium Embedded Framework (CEF) modules. There are no files on the server, so the action is repeated several times and every time the launcher is launched.
I submitted information via the support form. This does not guarantee a solution to the problem in the near future, so below is information if there are problems downloading about 56MB files.
Download CEF version 3.2924.1575.g97389a9
Windows 32-bit - for the root folder of the game;
Windows 64-bit - for x64 game folder in the root folder.
For each bit depth, place the corresponding files (from the log) in the appropriate places.
cef_extensions.pak, cef.pak, cef_100_percent.pak, cef_200_percent.pak, d3dcompiler_47.dll, widevinecdmadapter.dll, avcodec-53.dll and other missing files.
Use the skiprawdownload startup option (link to details in related topic) to further reduce startup time.
This is the manual fix for the OP issue. A couple of further details from my experience fixing it up.
AFAIK the launcher is trying to download version of libraries that DDO no longer uses and don't have available from their site.
You'll see all the failed files the launcher is failing to download in the launcher log (Use the Explore Log folder from the launcher menu.)
Code:
Error downloading http://installer.ddo.com/dnd//5000.0050.3264.4021//CEF3/2924/cef_binary_3.2924.1575.g97389a9_windows32/Resources/cef_extensions.pak
Error downloading http://installer.ddo.com/dnd//5000.0050.3264.4021//CEF3/2924/cef_binary_3.2924.1575.g97389a9_windows64/Resources/cef_extensions.pak
Download using Dolmatov's links the Windows 32 and Windows 64 versions of:
All Builds, Standard distribution 03/01/2017 - 3.2924.1575.g97389a9 / Chromium 56.0.2924.76
I was also missing the AwesomiumSDK 1.7.5.1 files and downloaded that to copy the files to DDO game folder.
Now on Launch, Admin access isn't requested and no attempt is made to download the files.
Another easier way (i realised after), like Valerianus suggested is to copy the missing CEF files from a working Lamannia (Preview) install.
If you are unsure, leave the install alone and hopefully DDO will eventually fix it, possibly with the new 64 bit server deployment.
It isn't actually downloading the files each time just trying to, waiting, receiving the error and moving on.