You'll need to try the solutions advised in the help article, @Roopa (just put VPN into the forum search engine) but if the steps don't resolve this, you'll have to wait for staff support, so after the weekend.
It may require a firmware update or a change of router.
Many similar cases listed, eg:
https://community.talktalk.co.uk/t5/Broadband/I-can-t-access-my-work-VPN-Zscaler-using-Talk-Talk-Bro...
Gliwmaeden2, a fellow customer.
From the 29th of March our TalkTalk Community will move to peer-to-peer support and the TalkTalk team will no longer be here to support with queries. Don’t worry we still have plenty of ways to reach out if you need to speak to TalkTalk directly. For more details check out the link in the post at the top of any forum message board.
