Users getting MFA errors

Question

To cut costs, my (small) organization has recently decided that I should admin our MS 365. We're about 10 people, so it hasn't been too much of an issue so far.

Due to concerns regarding phishing, I recently reset every employee's password. Now, several (although not all) of my colleagues get this error when trying to sign in: "MFA policy is misconfigured. Work with your admin to enable notification and verification code for mobile app in the policy. For more information, visit aka.ms/securitydefaults"

I've tried to mess around with the apparent settings in the org. MFA settings. So far, I've disabled MFA for the affected users.

I want to enable MFA again, though, so I'm hoping for some input on how to fix this issue.