Hi Danielarodrigues,
welcome to the Apple Community.
Re: Aren’t we able to install the new iOS updates in Brazil?
Am not aware of any reason why not, unless there are restrictions by the governing bodies in Brazil.
We are all Apple users, like yourself in this user-to-user community, so most of us would not know.
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Re: "trying to download and update it since 2021.And can’t."
We do not know which iPhone Model you have, and which iOS version is installed,
so also don't know if the latest upates are compatible with your iPhone.
iOS 16 and iPadOS 16 are compatible with these devices - Apple Support
iOS 15 and iPadOS 15 are compatible with these devices
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Re: What should do to get it installed?
Wondering what happens when you try to update your iOS ..
eg: update begins and doesn't complete / or an error message that would help troubleshoot / or etc ?
It is wise to always make a back-up of your iPhone data before you update.
You would need to update to an iOS version that is compatible with your iPhone model.
also: enough storage space on your iPhone for the update, and for your phone to operate smoothly.
You would also need iPhone to be well charged, and a strong internet signal.
You may need to use a computer for the update.
How to: Update your iPhone or iPad - Apple Support
Update your device using a Mac with macOS Catalina or later
Update your device using a Mac with macOS Mojave or earlier, or a Windows PC
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Troubleshooting:
Apple support's article: If your iPhone or iPad won't update - Apple Support
iPhone Support Team Website:
iPhone - Official Apple Support
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If needed: You may be able to access a computer at an Apple Store:
A reservation is recommended:
Apple Stores in Brazil
Rio de Janeiro
Barra da Tijuca, VillageMall
Avenida das Americas, 3.900
Barra da Tijuca, Rio de Janeiro22640
(21) 3179-3700
SP
São Paulo, Morumbi
Av. Roque Petroni Júnior, 1089
Vila Gertrudes
São Paulo, SP 04707-900
(11) 5180-5900
Hope there's something here that helps answer / solve the situation :-)