While I recognize that this problem has been asked before, I have attempted solutions from multiple different threads with no solution as of yet. 5 days ago when I was using Eclipse I had no issues whatsoever, now as of today I suddenly cannot auto complete 'sysout' with 'ctrl + space'. As far as I am aware, there were no updates to Eclipse.
I have gone through 'Window -> Preferences -> Java -> Editor -> Content Assist -> Advanced' and ensured that nothing was checked that interfered or conflicted with Eclipse being able to auto complete the java command, then reset to defaults. I checked that 'syso' was a listed and active template. I made sure that there was not another keybind that was conflicting with 'ctrl + space' Window -> ... -> Content Assist -> Advanced
Window -> Preferences -> General -> Keys
I did discover however that after I close Eclipse, and then open it back up, I can autocomplete 'sysout' once or twice, and then it stops and just pulls up the proposal context menu instead. The below gif does not show the proposal menu for some reason and I couldn't get it to capture, but it most definitely shows up with 'System.out.println();' as the only option: Attempting to use 'sysout' shortcut
Always try restoring the defaults on the 'Window -> Preferences -> Java -> Editor -> Content Assist -> Advanced' page, and if that doesn't fix it, try disabling that non-blocking option at the bottom. It's one of the few significant changes to the overall behavior in that area for a while.