The first problem I found with your formula is that it looks for the value of the last non-blank cell in the column. Well, you have percentage totals for each year so it is finding 23.5% in row 34 instead of the last value you really want in row 24.

I don't know why deleting the January value makes it work.

But ChatGPT is notoriously unreliable for solving tech problems. This is mostly because people do not formulate their questions in a rigorous way. If you get an answer from ChatGPT that doesn't work, don't bother to try to to fix it. Throw it away and get some real help.