Hello Donald,
I am using spectrum 10.4 which ships with “OpenJDK8U-jre_x64_windows_hotspot_8u212b04”
After downloading Oneclick.jnlp file, I found it is not opening with javaws.exe.
So pointed it to open with javaws.exe, by browsing C:\Program Files\AdoptOpenJDK\jre-8.0.212.04-hotspot\bin\ javaws.exe, and set default javaws.exe as default program for the oneclick.jnlp. now it is working.
Regards
Rohit