If you’ve added it to the WAF - > Tools → IP Access Rules, it should help
You should be able to track & trace down the challenged or blocked events under the Security tab → Events at Cloudflare dashboard for your zone at the moments when you share the link on the VK.com social media, and know exactly which security option was triggered. Could be Bot Fight Mode or Browser Integrity.
Once you find them, click on a particular one to find more details about it (user-agent, IP, HTTP version …). If yes, could you share some details which service was triggered that blocked you?
you should see your origin host/server IP out there, user-agent like WP-cron or WordPress/version, and ASN as well