“Thank you for your reply.: I’ve done the troubleshooting you’ve suggested. I don’t use VPNs and my devices are up to date.
I’ve even been in contact with Apple support to try and resolve this, but the issue still persists.“
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Troubles Logging into iCloud.com:
A. Clearing the the Temporary Files:
How to do so would depend on the browser. Here is how to do so on for Safari on an iPhone: Go Here: Clear the History and Cookies from Safari on your iPhone, iPad, or iPod Touch - Apple Support
B. Try Another Browser:
If it is officially iCloud.com, and not your Apple Account in Settings, then try using using another browser (ie Chrome or Brave)
C. Try Another Device:
What happens when you try logging in to iCloud on another device? Does this still occur?
D. Try Another User:
For troubleshooting purposes, create a new Administrator user and see if it then works.