I want to clarify that I am not a professional or anything....I am not affiliated with Microsoft or any other company. I just happened to have an issue, posted it, found the issue on google and repost on how I fixed it. I have tried to help those along
the way by doing the same thing for them. So by doing a quick search "new minecraft ps4 account already linked to ps4", this is what I have found that may help you...
This was found in a reddit that worked for someone...
Basically all i did was use a pc/laptop to access my Microsoft account and change my password. Whilst on the PC/laptop, use the browser on there to enter the linking code. And all done! Problem all solved my end
This was another one I found that worked for someone...
https://answers.microsoft.com/en-us/xbox/forum/all/unlinking-microsoft-acc-from-ps4-minecraft-bedrock/d72dbbb0-30bd-47ef-826e-e0c179b56d61
The following method worked for me and I was able to login with correct account. Login with the account already associated. Do not unlink Do not sign out Load the game Press PS button Then go to settings Go to storage
Click on Saved data
It will warn you that Minecraft will be shut down
Press OK
Select Minecraft
Select “Saved Data” file with cog
Press delete
Do the same with second file “Saved data” both have a cog
Once deleted do not restart PS just return to mine craft and sign in using a new login and that’s it. it is recommended you backup your saved games. also note that any activity since logging in with previous account will be lost. "
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This was also something I found...
There is an issue with new Microsft accounts and need provisioning on the Microsoft end before it will be fully functional. They take about a week to fully provision and be functional. It might be worth trying to log into an older Microsoft account to see
if you are able to log into it successfully. If you are able to log in successfully then we know that the issue is with new accounts and may take about a week to work. If you arent able to log in then maybe try some of the options above.
You can also contact Playstation or Microsoft. They might be able to help you.
I hope this helps.