DNS propagation can take a while, and there’s a tonne of places DNS records can be cached all along the way, from your computer, to your ISP, to your VPN service, etc.
If you’re using a proxied record (orange cloud), the change should be basically instantaenous. If you’re using non-proxied records (grey clouded), then in extreme cases, DNS propagation may take anywhere from a few seconds, up to 48 hours - your TTL on the records will have some impact here too.
Can you share any more information about your domain, the CNAMEs you’ve changed, etc.?
Check the linked thread below for more info about propagation, and how you can test the DNS from various places around the world.