Why can't I access this wifi access website

[Android Central Question]

Hi. I've recently switched to a Huawei P20 Pro and I can't access the website portal to sign into my corporate wifi. I've never had this issue with any other device and I.T says it's not their network. I just get a page that says THIS SITE CAN'T BE REACHED. Is it a device security setting? Wifi works everywhere else.
Please help