Hi @ep2012
All the plans, including the free plan, require a credit card in order to start, and have specific pageview limits and features available to them. You won’t be charged unless you upgrade to a higher tier.
It’s kind of like how you might be billed for internet service or a phone plan. Depending on the phone or internet package you choose, you might get more lines, gigs of data, or other additional features. If/when you near the limit of your selected package, they let you know they’ll be charging you if you go over so your service isn’t interrupted.
OptinMonster takes this same approach, so in the event, your account exceeds the campaign impressions available to it, your campaigns continue showing, and you can keep growing your email list, leads, and sales.
You can control on what happens when you reach the limits of the free plan as per this guide: https://optinmonster.com/docs/pageview-and-upgrade-preferences/
Also the plugin has been tested upto WordPress 6.3. If you are having any issues using that, please post the error so we can assist.