Hello, I've just received my Archer C80 today and I'm totally happy with the purchase.
It seems that a little problem appeared when I try to add port forwarding and exactly in the Internal Port, it said Invalid format, per example : 7000-8000

I tried all the method in the support link of tp-link https://www.tp-link.com/en/support/faq/1379/ per example : If you need to input a port range xx-xx when configuring the port forwarding, please leave the internal port empty. It said : not allow to be empty

Screenshots : Invalid format https://imgur.com/aFpPRZg             /               not allow to be empty  https://imgur.com/jWzwcdi
Hopefully you can solve my problem.
Thank you!