Usually it is an MTU size issue :

Please follow this link :  https://faq.draytek.com.au/2022/11/24/slow-connections-to-australian-ato-website/

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Typical issues experienced are:

  1. When trying to log into a portal, the page sits and spins for a long time before access is granted.
  2. Slowness connecting to certain websites which normally connect within about 5 seconds, but are now sitting on a redirect for between 30-60 seconds before connecting.
  3. Ping 8.8.8.8  works.
  4. Online Status>>Physical Connection shows a green WAN IP.

Solution

The issue is usually found to be the MTU size required for the WAN connection is too large.

Changing the MTU size to 1326 (try to reduce it from 1500 in chunks of 8) in the router WAN settings resolves this issue.

or follow this url :  https://faq.draytek.com.au/2021/03/15/adjusting-vpn-mss-mtu-settings/

Edited by HL March 2024