How to confirm I've “maintained” a Salesforce certification?

Try the below link. You can search by your name or email and it should tell you what certs are live for you.

https://trailhead.salesforce.com/en/credentials/verification

For salesforce certification verification, follow the steps below:

Visit the Trailhead Verification page.

Enter your Webassessor email beneath Certification Holders: Check Your Status.

Click Request and follow any subsequent prompts.

Your credential status will be sent to you in an email.

Here are the steps for Salesforce maintenance exams:

Go to https://trailhead.salesforce.com/en/credentials/verification.

Type your Webassessor email in the box on the right.

Check your inbox or other folders for new email from certification@salesforce.com.

See your current credential status. If you are behind on your maintenance exams, there will be a direct link to it in the email.

Click on the module link, and follow the instructions to complete your maintenance.

You’re done!