I have had this issue come up only a little bit ago (seems after the last client update). But I use CAPS LOCK as my push to talk key and I have for the past 6 years. All of a sudden now TS does not recognize me pressing that (or any other) button if I open a game like Mechwarrior Online (even before a match) or even just the steam window. It works in the League of Legends client (before a match) and works fine while i'm in chrome. Also works fine while I have teamspeak open obviously, but anything else and it stops. It also works fine if I put on voice activation all round, but I can't be the only one having this issue. I read a previous thread here where it was an issue with the identities but that didn't seem to fix it at all.