For the last 3 days I've been getting this error and kicked from my Realms server I bought about every 5 to 20 minutes.
Things I've tried to fix the problem:
Java Control Panel > Check box for "Enable the operating system's restricted environment (native sandbox)"
Uninstall / Reinstall
Windows Firewall allow all private
Flush DNS
I'm playing PC Java Edition realms on version 1.16.3.
Update: Uninstall / Reinstall after Flushing DNS did have some effect. I did get to play for a few hour span but the problem still comes back after a few hours.
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duplicates
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Thank you for your report!
We're tracking this issue in REALMS-5600, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
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I'm only saying this because I saw the post from "Ined" on the duplicated issue that you linked me too, but I am still having the same problems.
Everyone has been experiencing this for four or five days, but no answer from Mojang about it.