I wouldn't try without updating again.
Follow these instructions exactly:
- Follow the prompts to download and install the update, or force update via Settings > System > System Update. Do not reboot.
- When prompted to reboot, go into Magisk, then tap Install > Install to Inactive Slot. Magisk will prompt you to reboot; follow the prompts.
- Device should reboot into updated slot with root. If you get a failure message during OTA, go into Magisk, tap Uninstall, then Restore Images, before trying to update again.