I also can't get this to work at all. It's super frustating (and certainly not the only frustration I have with this Router!). I have followed the instructions to the letter.

The USB drive (Seagate Expansion 8TB) is not encrypted.

• I have tried formatting the drive with HFS+

• I have tried formatting the drive with ExFat

• I have tried creating a partition just for Time Machine, partition formatted with HFS+, then select that volume as "Backup Disk" in AX6000's Time Machine menu

• I have tried with default admin / admin username / password, and have tried updating it to something different

In ALL cases after selecting "BackupTM" in Time Machine, entering username and password, after about 30-40 seconds get the message:

Please advise on the fix. Does anyone actually have this working?

@MarkJC Were you able to figure out a fix? I'm having the exact same issue with an AX11000.

@Mostapasta Yes - I ended up not using the TP Link Time Machine "feature". Instead I created a sparse bundle on the drive, of an appropriate size, and then pointed Time Machine to that. There are a few gotchas. Just Google "Time machine on a network drive" and you'll find some help. I'd post a link I found helpful, but that is not allowed here 

@MarkJC Thank you!!!! 

@S-Cote I've been banging my head against a brick wall about this for ages.

The trick, that worked for me, was:

1. Connect the drive in question into the your Mac

2. In finder, on the drive itself, right click, select 'Get Info'

3. Select the group in the Pane called 'Sharing and Permissions'

4. Next to 'Everyone' change this from 'read-only' to 'read & write'

5. Click the '+' button and add under 'User & Groups' - 'Administrators'

6. Click seelct

7. Change the permissions on 'Administrators' to 'Read & Write'

Close

Eject the Drive

Plug it back into the Router and follow the kb article on how to setup time machine

Error message gone!

@matt_film 

I will definitely try that!

Thanks for the hints. It works well here, after changing the R&W access on the disk.

I am surprised that my external disk, which was originally mounted on an Airport extreme, is format which Apple format, and can be used 'as is' by the tp-link Archer. 

Are there any other things to try? I tried changing the R/W access and still get the same error message

Same problem. Changing the permissions did not help. Did anyone else have luck?