I figured out how to fix this. Want to post my solution in case anyone else runs into this issue in the future and wants to reference back.
On my Windows 10 PC, I was able to solve this by going into Windows Settings > Apps > Manage Optional Features. Then locating the “Japanese Supplemental Font” file. Note that it says install for me since I have already uninstalled it. It seems like it can be installed again at any time by selecting “Add a feature” from the top of the menu.
Once I uninstalled the file, and rebooted my PC. I came back to WaniKani and am now back to seeing all characters in the original font that was being used. I still do not know what font this is by name, but I really prefer this over Meiryo.
My PC went through some updates yesterday and I had to reinstall the Japanese Language keyboard. When I did this I believe I also installed other portions of the language pack that weren’t previously installed on my PC, including the additional fonts pack, which must be packaged in with the basic typing or handwriting packages on Windows 10.
Thank you all for the help on this matter, and apologies for any initial confusion I may have caused from my post.