Hi, I have pretty much the same issue.
Using Telerik 2016 Q2, the Datapicker popup does not shows under IE11, but it works OK on Chrome and Edge (it works OK in the Web demo app). Since I'm not proficient on Web programming, I have difficulties to fix this. The problem happens in my dev. pc, I do not have a production site yet.
After running the application I detach VS2015 debugger and then press F12 on IE11. The login page has some issues pointed out in the debugger and console, but after login to the application and opening the webpage that contains the datapicker there are not errors at all.
can you please shed some light to get this fixed? Thanks.