A2 hosting does provide you with web hosting services, correct?
You should receive the IP address of the web hosting / origin host / server from them.
Therefore, upon registering for an Cloudflare account and adding your domain to your Cloudflare account, changing domain nameservers at your domain registrar making sure to point them to the associated ones which were provided to you in the process of adding your domain name to your CF account, you’d have to double-check the DNS records which were scanned and possibly added automatically. Otherwise, you can always view and modify them as needed.
Furthermore, if you recently changed your domain nameservers, regular DNS propagation time usually takes up to 24-48 hours to complete.
May I ask have you tried using a different Web browser, or tried clearing your Web browser cache?
How about using a Private window (Incognito mode) or a VPN connection if possible?
Is it the same behaviour on your mobile phone (4G LTE, mobile data, cellular)?