1. Who is this pollster?
2. 0% undecided in September? Really?
Another question - apparently 200 out of 500 responses were by "mobile-app based technologies." What specifically is that, and is it opt-in? It sounds like something different from calling cell phones. Since apparently they don't weight by partisanship, my guess (though I emphasize that this is pure speculation) is that this poll could be including too many Beto supporters who are opting in, and that could be skewing the result.
Also note that this is a poll of "active voters" (i.e. registered voters), not any sort of LVs.
Interestingly, the person on the "who we are" page for the pollster worked at the RNC previously.
https://poppolling.com/who-we-are/If this is a partisan-affiliated poll, could it be that Republicans want the race to appear close in order to make Republicans think that it is close, because they are afraid Republicans won't vote otherwise since they think Dems can't win?