Every server gets a fresh IPv4 address. If the IP was on a blacklist before, we request removal right away. It may still take a few days for all networks to update.
Also, a newly purchased domain might need to build up some reputation first before the firewalls of the big dogs allow it to play with them.
Our mail setup (SPF, DKIM, DMARC, MX) gives you a near-perfect spam score. But providers like Google or Microsoft may still filter mails into spam at first. Usually, things settle within a few weeks.
You can send an email to https://www.mail-tester.com/ to check for any issues with the setup.