Did you open the Emscripten Command Prompt application from Start > Emscripten > Emscripten Command Prompt? If so, within the command prompt type “emsdk install” without the quotations. After the information has populated, please then type in --old more information will appear and please wait for it all to populate. Then type “emsdk activate ‘version number’” for example: C:\Program Files\Emscripten>emsdk activate sdk-1.29.0-64bit
Once that is complete, your Emscripten should be up to date but please remember to also update your environment variables as follows:
Value: C:\Program Files\Emscripten\emscripten\1.29.0 (or wherever emcc.exe is location)
Value: C:\Program Files\Emscripten\clang\e1.29.0_64bit (or wherever llvm.exe is location)
Value: C:\Program Files\Emscripten
ode\0.10.17_64bit (or wherever node.exe is location)
Value: C:\Program Files\Emscripten\python\220.127.116.11_64bit (or wherever python.exe is location)
Please keep in mind that Unreal Engine 4.9 should not have the same troubles with Emscripten as 4.8, so when you upgrade to 4.9 once it’s officially released, it should be quite a bit easier to use.
I hope this information is useful to you. If you happen to run into any further complications, feel free to post on AnswerHub as well. Have a great day!