Error 64 when flashing OpenGapps

One Gapps (pico and nano) errors with 64 when I try to install using twrp-3.3.1.4. I know I'm using the right version. I'm on a brand new One Plus 7 Pro. ############################## _____ _____ ___ ____ / _ \ | __ \ / _ \ | _ \ | / \ || |__) | |_| || | \ \ | | | || ___/| __/ | | | | | \ / || | \ |__ | | | | \_/ \_/ |_| \___| |_| |_| ___ _ ___ ___ ___ / __| /_\ | _ \ _ \/ __| | (_ |/ _ \| _/ _/\__ \ \___/_/ \_\_| |_| |___/ ############################## Open GApps nano 9.0 - 20191017 - Mounting /vendor find: /system/system: No such file or directory ls: /system/system: No such file or directory - Gathering device & ROM information ***** Incompatible Device Detected ***** This Open GApps package cannot be installed on this device's architecture. Please download the correct version for your device: arm ******* GApps Installation failed ******* - Copying Log to /sdcard - NO changes were made to your device Installer will now exit... Error Code: 64 cp: can't stat '': No such file or directory ls: /system/system: No such file or directory cp: can't stat '/system/system/etc/g.prop': No such file or directory cp: can't stat '/system/system/default.prop': No such file or directory cp: can't stat '/system/system/build.prop': No such file or directory cp: can't stat '/vendor/vendor/build.prop': No such file or directory cp: can't stat '/data/local.prop': No such file or directory cp: can't stat '/build.prop': No such file or directory cp: can't stat '/system/system/addon.d/70-gapps.sh': No such file or directory cp: can't stat '/cache/recovery/log': No such file or directory __bionic_open_tzdata: couldn't find any tzdata when looking for CST6CDT,M3.2.0,M11.1.0! __bionic_open_tzdata: couldn't find any tzdata when looking for posixrules! - Unmounting /vendor Updater process ended with ERROR: 64 I:Install took 9 second(s). Error installing zip file '/sdcard/open_gapps-arm64-9.0-nano-20191017.zip' Updating partition details... I:Data backup size is 0MB, free: 227550MB. I:Unable to mount '/usbstorage' I:Actual block device: '', current file system: 'vfat' ...done I:Set page: 'flash_done' I:operation_end - status=1 I:TWFunc::Set_Brightness: Setting brightness control to 5 I:TWFunc::Set_Brightness: Setting brightness control to 0