Paper Sizes (other than US Letter) not available

I recently downloaded Grammarly on my MacBook Air, operating on MacOS Catalina Version 10.15. After using it for a few hours, I realized that my default paper size when printing became US Letter. I typically use A4. So when trying to print, the printer detects that it is a different paper size, and asks if I want to proceed. I try, but the margins are all off because the laptop wants to print in US Letter but the printer can only print in A4.

There are also now no other options for paper sizes under Layout > Paper Size in Word for Mac. I have since uninstalled Grammarly and Word for Mac, and reinstalled it. No change.

I noticed that there is also no more options for me to print on Preview either.

There are paper size options in Excel, but the printer still detects the paper size as US Letter. I suspect that it is no longer an app issue but something that has been "embedded" into my system, to some extent, when I downloaded Grammarly (?). I've also reinstalled my printer, to no avail.

I have set the default paper size on Word for Mac and in system preferences. It says A4, but when I want to actually print any document, it goes to US Letter.

I've gone to this website https://themacadmin.com/2012/01/16/setting-a-default-paper-size/ which apparently allows you to maneuver the default paper size through Terminal, but I can't seem to get it to work. Any help would be appreciated - I'm going out of my mind and it's affecting my work.