My SPF is not getting validated, how can I validate it?

As per the standard timelines followed by DNS service providers, the DNS records are reflected globally with in 30 mins to 1 hour time.
You can re-validate the DNS settings from your DNS panel with your provider to verify if it is configured correctly as required under Netcore Email API sender domain settings. Once it is setup properly, wait for 30 mins to 1 hour to let these DNS changes reflect globally and then click on "check DNS records now" button available under sending domains => view settings option

Once the panel moves to verify stage, your domain moves to approval stage, where we manually validate and approve it. In case of any assistance required while setting up the DNS records, you can refer to our documentation below or connect with us on 24X7 live chat,

Configure Netcore Email API DNS settings on Godaddy (https://emaildocs.netcorecloud.com
/docs/how-to-do-Netcore Email API-dns-settings-with-godaddy)
Configure Netcore Email API DNS settings on Hostgator (https://emaildocs.netcorecloud.com
/docs/how-to-do-Netcore Email API-dns-settings-with-hostgator)
Configure Netcore Email API DNS settings on cloudflare (https://emaildocs.netcorecloud.com
/docs/how-to-do-Netcore Email API-dns-settings-with-cloudflare)
Configure Netcore Email API DNS settings on bluehost (https://emaildocs.netcorecloud.com
/docs/how-to-do-Netcore Email API-dns-settings-with-bluehost)
Configure Netcore Email API DNS settings on namecheap (https://emaildocs.netcorecloud.com
/docs/how-to-do-Netcore Email API-dns-settings-with-neamecheap)