some website Clients get this page
Access Denied
Error code 1020
you don’t have access to “my website”.
this site owner may have set restrictions that prevent you from accessing the site. contact the site owner for access or try loading the page again
why this happened to my site and how can i fix the problem ?!
Greetings,
I am sorry to hear you are experiencing an issue with Error 1020.
If these are your websites and you experience 1020, you have to check Firewall tab to troubleshoot and find any clue why it happens.
If you got 1020 error, you should see blocked requests/events when you navigate to the Firewall tab → Overview for each of your domain names at Cloudflare dashboard .
Therefore, check for “service” to see what blocked your request.
Can you share a screenshot of your Firewall Rules?
Kindly, may I ask you to share your domain name and/or the URL with which you are experiencing 1020 error so I could try to access and provide feedback to you about it? 
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)?
Helpful articles which contain useful information articles about 1020 Access Denied error page can be found below:
I get this message
You currently have no firewall rules. Please click on ‘Create firewall rule’ to get started.