Are you using a proxy and is the proxy slow ? Look into this part. Yes, it may sound weird, but the issue you mentioned happens when the internet is slow, which would mean a slow proxy if a proxy is used, even though your actual internet connection would be fast. A workaround would be : be logged into the respective GAds account and open another tab in the same browser and go to google dot com and search "Google Ads appeal form" and see the 2 links in the screehshot attached, from these 2 links you can go and get to the usual GAds appeal form.
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