I understand that you are having difficulties removing a greyed-out tile from your Windows timeline, despite following the suggested solution of deleting the files in the "C:\Users\<UserName>\AppData\Local\ConnectedDevicesPlatform" directory. I apologize for any frustrations this may have caused.
While deleting the files in the mentioned directory should typically remove the associated tiles from the timeline, it seems that in your case, the tiles reappeared after you deleted the files.
In addition to the directory you mentioned, there are a few other locations where data related to Windows timeline may be stored. You can try deleting the files in these directories as well:
1. C:\Users\<UserName>\AppData\Local\Packages\Microsoft.Windows.Cortana_<some_long_string>\LocalState\
Please look for a "default" folder in this directory and delete its contents.
2. C:\Users\<UserName>\AppData\Local\Microsoft\Windows\ActivityFeed\
Delete all the files within this directory.
After deleting the files from these directories, restart your computer to give Windows a chance to rebuild the necessary files. Hopefully, this will remove the greyed-out tiles from your timeline.
If the issue persists, there might be a more complex underlying problem with your Windows installation. In such cases, I recommend seeking further assistance from Microsoft Support or visiting the Windows community forums where experts and other users may be able to provide more specific advice based on your situation.
I hope this helps, and please let me know if you have any further questions or concerns!