Like and Dislike Buttons on Post with Counter – Only allow one click per post per user session

Working on a “Like” vs “Dislike” for blog post in WordPress. While all is working fine, the intention here is to make it work for guests and logged in users, but more importantly; to only allow one click (Like or Dislike) per post from the same user (trying to understand if I can use WordPress sessions here?).

filemtime(): stat failed warning within a child theme

I am trying to work on my child theme, but I can’t get rid of the filemtime(): stat failed warning, which appeared as soon as I activated my child theme.
After reading other questions, I understand that the filemtime warning is often caused by incorrect use of URLs and paths. However, I think I provided URLs and paths correctly, and if that’s the case, then there is something else I’m missing.