s_1234 Said:
"I can not update my MacBook air 13 inch 2017 to Big Sur 11.5.2: [...]The internet connection is excellent and stable but still cannot update to BigSur 11.5.2"
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What to Do:
Can you visit other sites (i.e. google.com) just fine? If so, then that means there is an error connecting to Apple's servers. So...
Create a Temporary Admin:
See what happens when you use a new administrator to install this. If it works, then there is an error in your current user.
Try this in Safe Mode:
If you can't click something, then try it in Safe Mode [Hold Down: the shift key upon boot]. In Safe Mode, Login Items do not open at login; certain preferences are set aside; and damaged system files (i.e. caches) are fixed. Go Here: Start Up your Mac in Safe Mode - Apple Support
Use Ethernet:
On the computer, you connect it through Ethernet, going directly into your router. For a Mac (or PC) that does not have Ethernet, this would be the adapter to use: Belkin USB-C to Gigabit Ethernet Adapter - Apple