Though I have a Libre5 folder in my Program files, I cannot open any files with either the shortcut or “Open with” in Properties. I have many documents in my Doc file, but now will open with Libre. This just happened this afternoon.
Although you don’t say it, it sounds like you are using the Windows 10 operating system and that you just did an update (intentionally or otherwise). Search the forum for Windows 10 problems – I expect several of the offered solutions will be useful to you.