The restrictions on VPN access stem from a variety of factors,which can be summarized as follows:

1. Content Restrictions: Certain websites, such as those that only display ads or low-quality content, may be blocked if the VPN is attempting to access them.

2. Privacy Policies: Websites often have privacy policies that restrict access to specific content or require certain user actions, which may prevent VPN access.

3. Server Reliability and Maintenance: If the servers hosting these websites are down or not functioning properly, access may be blocked.

4. Performance Issues: Some websites may require specific software or high-speed connections to load, which could prevent VPN access.

5. Technical Problems: Outdated software or protocols used by the VPN may not function correctly, leading to blocked content.

6. Purpose of Use: Users who access VPNs for work or personal use may encounter specific restrictions due to company policies or site requirements.

7. Device Compatibility: If the device being used by the VPN lacks necessary updates, it may not function properly, resulting in blocked content.

8. Usage Patterns or Errors: accidental blocking of a website or use of outdated VPNs may lead to blocked content.

9. Legal Considerations: If websites or content violate privacy laws or copyright laws, the VPN may be blocked to protect users' privacy or comply with laws.

10. User Errors: Technical issues or errors in usage can result in blocked content.

In conclusion, the blocked access to VPNs is often due to a combination of technical, legal, and user-related factors, each contributing to the restriction on access.