Note that you can’t open portals during the Heist or Grand Heist. You can see the image below: Portals are disabled here.
Grand Heists are performed using Blueprints. Before you can start a Grant Heist, you must plan for it at the Planning Table. Once you have a confirmed Blueprint and paid the fees, you can open a portal to the Grand Heist location.
While you can’t open portals during the Heist or Grand Heist, you may freely leave and re-enter the Heist portal before the alert is raised.
Note you must enter the heist instance itself, not just the portal room, before you can leave without closing the portal.
You may leave and re-enter the portal in between each wing as well.
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