@JAPierce 

Google "windows 10 administrator user can not write to hard disk, hidden administrator can" and this appears to have many hits, and check the AI Overview.

Are you on W10 Pro, if so, this could be the cause:

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Check group policy settings: Group Policy settings configured on your system might restrict write access to external media. If your computer is part of a domain or managed by an organization, the group policy settings might be enforcing certain restrictions. Contact your system administrator or IT department to verify if any such policies are in place.

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I am on W11 Home, Wife on W10 Pro, we both do NOT have your problem.

Both of us run as Administrator (can check via Control Panel, User Accounts) with wife running with the only difference being Account Control Settings. Mine is NEVER, while my wife's is set higher. I would not think that matters?

Looking at the above suggestion, it might be 'it'?

I don't have GPEDIT, but I did find this way to check/change it (again, I'd post the link but TP Link doesn't allow that so I copied the REGEDIT part of the answer):

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Disable the use of USB storage devices by Registry Editor Step 1: Open Registry Editor in Windows 10 by running regedit in the Run dialog box. Type regedit in Run box Step 2: Go to Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\USBSTOR, and then locate the DWORD value named ''Start'' on the right-side pane. The default value data of Start is ''3''. Double-click on Start, and set its value data to ''4''. Change value data Step 3: Restart Windows 10 for the changes to take effect. This will prevent any USB storage device from connecting to the computer, and thus disable the use of USB storage devices on the computer. Note: By Registry Editor, you just disable the use of USB storage devices, but it won't affect the use of USB mouse, keyboard, and printer on the computer.

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I checked my START value and it is 3, if 4 on your PC, that could be the problem?

If your setting is also 3, you might consider going to a Windows 10 forum and post there?

  @IrvSp 

My setting is also a 3

At this point I did a full reformat of the drive (long format) as NTFS

I used chatgpt to try everything under the sun.

I've even upgraded to windows 10 Pro from home

The ONLY thing that works is the chatgpy had me create a temporary new profile, guess what the new profile works perfectly, I can drag drop write etc to the drive everything works great.

So what is the difference between the profiles?  ugh I really dont want to have to go thru and setup a brand new profile.

I even ran a scan and repair on the old profile, windows found some things and repaired them but still no write access.

I can even create a brand new file on the drive and delete things, why cant I copy/paste to it?

So bizarre

  @JAPierce 

I am running out of thoughts here, but is you open a CMD prompt as an Administrator you can run this command, "wmic useraccount list full". It will show you all the UID's and the 'data' associated with them. Can add a '> filename.txt' to the end to write it to a disk file for easier reading.

I am also suggesting it might NOT be UserID related but something you are Auto-starting. A program like AUTORUNS (part of MS's Sysinternals suite) or AutoRun Organizer, will show what your UserID is loading at boot time. In either program you can disable or delay starting.

To actually determine if one that autostarts could be the cause possibly, boot into SAFE MODE and see if your USERID can write to the drive. If it can, then it probably is something starting causing the problem. 

So Reboot, and then you could then determine which one by disabling 1/2 at a time using one of the above programs or even Task Manager on the Startup tab on the left. First time disabling, if it can write, re-enable one half of what you disabled. Can't write, then disable 1/2 of those left, repeating this until you locate the culprit. By trial and error you can locate the culprit.

  @IrvSp 

Hi again!  Just wanted to update you that Im STILL battling this problem.

Safe mode = no difference

New Windows admin profile: No difference

I reformatted the drive in NTFS and tried exFAT: no difference

I tried stripping off any windows ACLs or exif and file permissions from a files that wont copy: no difference

Using ftp access, there are no issues whatsoever. Unfortunately I cannot always use ftp.

Oddly, on a windows 11 machine, no issues whatsoever. Same thing for an android device, no issues.

I've been back and forth with TP-LInk support staff including one of their engineers, hopefully they'll be able to help decipher this, just wanted to update you.

Jeff