I believe this also happened with 6.2 and I had to completely reinstall but I am unable to download the patch. The first small download will work then once it says "downloading ffxiv" I'll get the following:

Unable to update patch files.
[11005][20815][20866][19900][5]
D:/Programs/FFXIV/SquareEnix/FINAL FANTASY XIV - A Realm Reborn/boot/locales/fileinfo.flin

Running Windows 10, have restarted, disabled some security on Windows Defender and Microsoft Edge, run the launcher as admin and tried to set the program folder as not Read Only (it keeps reverting). DNS changes did not help last time.

Any help would be appreciated!