Ok, sorry for the delay in answer.
Ignore the last update I did, the first problem was fixed (icrement bug), the second (last showing "?????????" rather than the actual date) was a problem with MediaWiki's database generation.
Like I said before, i'm brazilian, my wiki is in Pt-BR, we have accent in the words, so we use UTF-8 unicode-ci, but MySQL was configured to generate databases with UTF-8mb4 and this caused the second error.

Another update, I solved it, it was not a problem with MySQL, but the code started to work and was overwritten the "last" column on MySQL.
SO, I think I've found the source problem: the table need to have at least a value in the "last" column to start generating a correct value, so, if you have another account, it you bug again.
For this I continue with the temporary solution, changing the SpecialUserPageViewTracker.php(28-30) to not have the $last overwritten.

Ok, I solved the error above, this error is caused by the SpecialUserPageViewTracker.php(29) where you miss 2 square brackets around the 29 line.
When I changed it the error is gone, but the timestamp continue borked with the question marks (like in the screenshot).

@Sophivorus Hi! Sorry for the delay to answer you, i downloaded the latesd version of UserPageViewTracker, but i got a error in my main page: