Connection check failed:

1. The IP type, IP address, port, username, or password may not have been entered correctly.

2. The IP itself is inaccessible; try using a different IP.

3. Confirm the usage environment of the IP. Most IPs require an overseas environment to function.

4. Unstable or poor network conditions may also cause connection failures. Try reconnecting several times.

5. Check if there is an IP whitelist. If so, add the local IP to the whitelist in the proxy backend.

6. Verify if there is a limit on the number of connections for the IP.

7. Contact the IP provider's customer service for assistance.

Webpage cannot be opened after a successful connection check:

First, test whether it is an issue with the local network or the proxy IP network:

1. Without setting up a proxy IP, open the browser to check if webpages can load normally. If they load properly, the local network is fine. Otherwise, it indicates an issue with the local network.

2. If a proxy IP is set up but the webpage cannot be opened, it indicates an issue with the proxy IP. You can try the following solutions:

(1) The IP may require an overseas environment. Use a VPN or proxy with global mode enabled.

(2) Unstable or poor network conditions may be causing the issue. Refresh or retry multiple times.

(3) If the browser prompts for account credentials again, it indicates the IP has expired or is not configured correctly. Contact the IP provider's customer service for assistance.

(4) If certain websites cannot be accessed, consult the IP provider's customer service to check if specific website access is restricted.

Note: 

Since SupLogin itself does not provide network connectivity, it does not restrict access to any websites. Browser speed depends on the local computer's network speed, or if a proxy IP is set, it depends on the proxy IP's network speed.