Extremely low email campaign open rate

Hi everyone,
We used Klaviyo for years (and Shopify Email for a few months) in the past, then last month migrated our 70k+ subscribers to Brevo (on a shared IP). After weeks of setup, we sent out our first email campaign today (essentially using the exact same setup as before: validated domain, a list with proper subscribers only - that we actually cleaned before migration).

Our campaign today got 6% open rate, that might climb up by 9-10% by the end of the week, but nowhere near our previous fairly standard 30-35-40% open rates.

After this, our account got suspended and will be permanently suspended if it happens again :thinking: despite we paid for a whole year last month.

I was just wondering what do I need to check to resolve this ridiculously low open rate, does anyone have an idea why this has happened?

Thanks!

Just had the same issue.
Work emails going out to B2B customers.
went from ranging between a 25%-65% open rate to 4.97 and 2.97%.
I’ve checked with spam filters and nothing’s shown up.