Starting about a week ago (11/30/2017) I noticed that ctrl+shift+space was no longer working in visual studio (any version) to show the parameter info of a method invocation. I did quite a bit of searching to figure out the problem, especially here on SO, and I couldn't find a solution. I also double-checked my VS settings and even reverted back to an old settings file.
I methodically started closing applications to see if another application was stealing the input. My hunch was right and it turned out to be the Microsoft Teams desktop application. It turns out that Teams already has a similar bug open about shortcut keys related to the Polish language not working correctly when Teams is running. Those details are here: https://microsoftteams.uservoice.com/forums/555103-public/suggestions/32265802-alt-a-and-alt-s-affecting-polish-character-for-%C4%85
Within the above link there is a link to a beta build that fixes the problem for Polish, and it turns out that it fixes the problem for the ctrl+shift+space shortcut too.