After some searching, it appears someone who was also getting the R-3 error was able to install after rebooting their machine (Install Fails with Error Code R-3 - Getting Started & Setup - Epic Developer Community Forums). Can you let me know if that helps? If you still have problems getting the engine to install, please visit http://help.epicgames.com/ for technical support, here you can find information and solutions for common issues, as well as a contact form if you still need additional assistance.
Rebooting the machine definately does not help. I’ve been having this issue since 4.11 came out and was waiting to see if a solution is found somewhere. Since it seems to be an uncommon problem I figured posting a quesiton about it might help making it more visible. The standard fixes in the troubleshooting guide like reinstalling vc++ and net framework didn’t help either.
I’m sorry that didn’t help. To get in touch with Epic’s support staff for the Launcher, please visit http://help.epicgames.com/ and click on the ‘Email us’ link on the right side of the page. If you share all information and solutions you have attempted, our staff will continue to work with you to identify a proper solution.