@bontokiz 

What browser are you using? Is this hosted on Omada or an externally hosted captive portal? I just built mine out using the guide by TP Link and it works fine. I am using 5.3.1 on Debian.

Omada Hosted Captive Portal Guide:
https://www.tp-link.com/us/support/faq/896/

Externally Hosted Captive Portal Info:

https://www.tp-link.com/us/support/faq/2907/

  @FreeSamples 

I tried Chrome, Edge, Firefox and even the built-in browser from iPhones when connecting to hotspots. I think there might be a bug when uploading ZIP file. It gets uploaded but gives the error of browser not supported. Uploading a single HTML file works though.

  @bontokiz it may be worth walking through you process to give those reading this thread some more information. I am going to make some assumptions here:

- You are doing a locally hosted Omada Captive Portal

- Authentication - Unknown

- You are attempting to do an "import customized page"

- Original and Promotional URL options may or may not be enabled

- I assume if you are able to get this far into the configuration that you are able to connect to he wifi and when you attempt to login you see the error? Or is it at some other point in the process?

You mentioned that you are not able to upload a zip file and only the HTML. This sounds like it may be an issue with the site developed or the data in the zip file. Are you using .zip format or something else like .7z? I was able to download the demo information change some of the items and add some code. Then reupload the zip file to the Omada controller. It seems to have worked fine. I am not a developed by any mean, but the feature does not seem broken with my edits.

  @FreeSamples 

I agree, the scenario wasn't clear.

I'm using a software controller hosted on DigitalOcean. Access and management of devices are working fine. It's the hotspot that I'm having issues. I'm using Voucher as the authentication though I tried each authentications for troubleshooting but gives me the same problem. My issue is with the customized page. I can upload both zip and html files with no errors. Uploading an HTML file works, I mean when I connect to the WiFi and get redirected to the captive portal, I get this "..not supported browser" error. I don't get this when uploading just a HTML. I don't think its a problem with my files because I also tried uploading the demo.zip that you can download from the portal and it also doesn't work. My files is simple, just HTML, JS, and CSS. And this was working prior to updating my controller. So I think there's a bug on the controller. I may try reinstalling the controller.

  @Hank21 
 

1. Ubuntu 20.04 hosted in DigitalOcean

2. Yes I've tried all browsers even built in ones gives the same error. 
3. tar.gz

I tried reinstalling the controller but i get the same issue.