Why didn't Okabe realize he was in the Steins;Gate worldline? Wouldn't his trip to LA to see Kurisu in the OVA confirm to his mind that he's in the S;G worldline?
It's not that he didn't realize, it's that it didn't seem all that different to the other world lines aside from all the deaths and that pretty much just triggered his PTSD. He needed something to happen that was vastly different from the other world lines so he could disassociate them better.
This is also why Kurisu had to go so far back in time, because Okabe's mind was already messed up by the time he made it to Steins Gate in 2010.
Did you not watch the movie? They explain it expressly in the lab why he is having trouble with it.
hm OP made a post about the movie's plot, did he fuckin' watch it? durr
I don't even know how to respond to your stupid.