Why can't I access this wifi access website

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 :)

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