A 1020 error is a Cloudflare-specific error code for:
"Access denied."
Traffic was blocked by a Firewall rule within Cloudflare.
Resolution
If you are not the website owner:
Provide the website owner with a screenshot of the 1020 error message you received.
If you are the website owner:
Retrieve a screenshot of the 1020 error from your customer
Search the Firewall Events Log within the Overview tab of your Cloudflare Firewall app for the RayID or client IP Address from the visitor’s 1020 error message.
Convert the UTC timestamp of the 1020 error to your local timezone when searching in the Firewall Events Log.
Assess the cause of the block and either update the Firewall Rule or whitelist the visitor’s IP address in IP Access Rules.