Model :

Hardware Version :

Firmware Version :

ISP :

TL-WDR3600 configured as a WAP, wifi access is working, ADMIN UI is not working.

The admin management function of my TL-WDR3600, configured as a wireless access point, is no longer accessible.

This WAP device has provided good connectivity and control for the last 3 or 4 years, until I recently updated the firmware (Feb 2018).
The firmware updated to was TL-WDR3600_V1_150518. This was dowloaded from UK site. I believe it is the lastest available.

I have a home LAN providing ethernet access to Win 7 PRO PC and WIn 10 Home PC and wifi access to Win 10 Home laptops, Chromebook, RIM Playbook, Samsung and Sony phones.
Visitors have also used the wifi with a variety of devices without any issue.
All devices on my LAN are configured with fixed IP addresses including the WAP.
The WAP is connected to my router via ethernet cable, LAN port to LAN port.

After the firmware was updated, wireless access still works fine for all devices, as before.
Before the update, I could access the WAP management function over wifi or over ethernet by typing its fixed ip address into browser URL.
My preferred browser is Firefox, but I have also used IE and Chrome to access WAP management previously.
Since the update, neither method works any more via any browser.

TP-Link's firmware update notes suggest that after update is completed:-
'Step 5 It is recommended that restoring the device to factory default to make the new functions take effect; Click System Tools->Factory Defaults, Click Restore Button.'
I have not been able to try this and anyway, I am reluctant to lose my current configuration as wifi access still works and because
I have read on forums that some users have not been able to log in after firmware upgrades as default admin/password is changed.

I should have adhered to the old adage 'leave well enough alone'.
Can anyone suggest a solution?