Sorry for the double quote, here is some more info I found and I hope it helps!
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"SLoP (really, does anything think about acronyms when naming these things?) uses Universal's Virtual Line virtual queuing system. So - in normal operation - there would be no physical queue in front of the attraction entrance at 3637 Pets Place on Universal's Upper Lot. To ride, reserve your ride time in Universal's official app, or scan your park admission ticket at the subway station next door to get a time. Then just show your QR code to the doorperson and you will be welcomed into this upscale Manhattan apartment building."
The subway station they refer to, I believe is just to the left of the attraction entrance.