Can't reach tenant but nothing's wrong

[Michael D.]

I own a rental house in another state. The tenant and I have always gotten along fine, corresponding via email, text and cell phone. On occasion she's been a little difficult to get in touch with, but I've always gotten a call back in a week or two max - until now. This is a low-end rental and a low-income (but good) tenant.

I tried to call her about a a minor issue several months ago, and have not heard back since. I've tried emailing several times, texting, and calling her cell phone. Recently I've tried sending a certified letter (containing all my contact info and a request for contact) with return receipt, but USPS reports they were unable to deliver it  - Notice Left (No Authorized Recipient Available)

There is nothing particularly wrong, and she's completely current with rent based on auto-payments.

I feel uncomfortable not being able to reach her. Is she traveling? Dead? Fine but won't talk to me? Also I'd like to resolve the minor issue, but it's not pressing.

How should I proceed? Do nothing? Hire a person (manager?) to pay a visit? Any other ideas or advice?

Thanks!