For the phones they have with the MetaNav, the main enemy is going to be battery power: Technology like phones will behave as normal (minus having reception) until the battery dies.
If they try to use the app itself while their phone is still charged though, it'll almost seem like it's going to work and do something; the Nav will work pretty much as usual, say all the same stuff as it normally would, but the main difference is it won't take them to the Metaverse. (For example, let's say they wanted to change one of the court rulers' hearts, even if they figured out the Palace's location/distortion, they'll only be able to get to the point where they'd normally navigate to it. The MetaNav will essentially register them as already having arrived at wherever they were supposed to go.)
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If they try to use the app itself while their phone is still charged though, it'll almost seem like it's going to work and do something; the Nav will work pretty much as usual, say all the same stuff as it normally would, but the main difference is it won't take them to the Metaverse. (For example, let's say they wanted to change one of the court rulers' hearts, even if they figured out the Palace's location/distortion, they'll only be able to get to the point where they'd normally navigate to it. The MetaNav will essentially register them as already having arrived at wherever they were supposed to go.)