Question :
I have a 2019 MacBook Air and when I tried to install the latest macOS system update, it froze… I called Apple, and they told met to reinstall macOS, but evert time I turn my Mac off and back on with the OPTION+SHIFT+R key-combo pressed on my keyboard, I run into a black screen with a light grey globe with a white triangle with an exclamation mark in it (a warning icon) and a text below it that just says “support.apple.com/mac/startup -2101F”

What can I do to fix this ?

Answer :
The -2101F error message that you are getting means “cannot connect to the internet”, and connection to the internet is essential for your Mac to do a regular reinstallation of macOS nowadays…
There are some options to solve this problem. First try this one :
– check if your WiFi internet is working properly by connecting to your WiFi using your iPhone (or any other mobile phone)
– if it turns out that your WiFi is not functioning properly, restart your modem to make sure all lights on it (like “Power”, “Internet”, “LAN” end “WiFi”) start blinking
– then restart your Mac and try to initiate the reinstallation process again

If that didn’t help, try this :
– connect your Mac to the internet using a UTP/Ethernet-cable
– for this, you need a UTP/Ethernet cable that is has connection to your modem (preferably directly)
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– if you don’t have a UTP/Ethernet-cable, you can borrow one or buy one
to buy one from Amazon US, click here
to buy one form Amazon UK, click here
to buy one from Amazon DE, clcik here
– modern MacBooks don’t have a dedicated UTP/Ethernet-port, so you will need a UTP/Ethernet-to-USB(-C)-converter-cable also
– if you don’t have a UTP/Ethernet-to-USB-C-converter, you can borrow or buy one
to buy one from Amazon US, click here
to buy one form Amazon UK, click here
to buy one from Amazon DE, clcik here
– if you have a UTP/Ethernet-to-USB-converter-cable, but you only have USB-C ports on your Mac, you will need a USB-C-to-USB-converter also
to buy one from Amazon US, click here
to buy one form Amazon UK, click here
to buy one from Amazon DE, clcik here
– after you have connected your Mac to the internet using a UTP/Ethernet-cable, restart your Mac and try to initiate the reinstallation process again

If that didn’t work, try this :
– connect the UTP/Ethernet-to-USB(-C)-converter-cable to a different port on your Mac, because sometimes that USB/USB-C port on your Mac may be faulty, misfunctioning of broken
– then restart your Mac and try to initiate the installation process again

If that didn’t work, try this :
– make sure that one of the USB(-C) ports on your Mac is functioning properly by connecting a USB-mouse or USB-keyboard or USB-stick with a light in it (you might also need a USB-C-to-USB-converter-cable for this) and check if the light is switching on
– if the light in the mouse, keyboard or USB-stick doesn’t turn on when connected to your Mac (do make sure that the light is actually working when using it on another computer), your USB-port is broken and you will need a hardware repair (or a new Mac, which might be more tempting in a lot of cases)
– if the light does turn on, disconnect the mouse, keyboard or USB-stick and use that USB(-C)- port for the reinstallation of macOS from a USB-stick
– first you will have to create a USB-stick with a macOS-installer, to do this, you will need another Mac that is the same age or newer than your Mac and if your Mac doesn’t have an M1/M2/M3-or-newer processor, you will need an Intel-based Mac for this
– follow the directions to create a USB-stick with a macOS-installer that are outlined here :
https://www.macworld.com/article/671308/how-to-create-a-bootable-usb-macos-installer.html
or the instructions from Apple itself :
https://support.apple.com/en-us/101578
– if you don’t have an empty USB-stick at hand, you’re best of buying a 32GB USB-C-stick
to buy one from Amazon US, click here
to buy one form Amazon UK, click here
to buy one from Amazon DE, clcik here
– after you have created the USB-stick with the macOS-installer on it (on the other Mac), plug the USB-stick into your faulty Mac (make sure you use the USB(-C)-port that you know is working) and restart your Mac and initiate the installation process

That’s it !

enjoy 😉