There are two ways to disable indexing;
- a theme edit for manual control of robots.txt;
- and a plug-in that also does this, though that is quite new.
Maybe you had one of those options in use?
To double check these are the known ways to look;
- the Archive page on your site;
- the search on your site (which uses the Archive);
- and the settings-based Posts search.
Those usually get the job done for me but I’m unsure if they can work well for everybody.
I don’t know how Google’s indexing works but I have seen people talking about it being delayed or inconsistent. I think there’s a way to check, maybe some sort of Google console for it.