Photography / Image Rights | client reselling my photography

I publish illustrative scenarios prepared by my practice. All participants and conversations are fictional. The fictional posts are not posts by real users, accounts of client experiences, or reports of actual results.
Illustrative scenario prepared by my practice.
For informational purposes only. This is not legal advice. Laws vary by jurisdiction. Consult a qualified attorney for advice specific to your situation.
Hypothetical question

Has anyone dealt with something like this? I'm not sure what my options are.

client reselling my photography. I've been dealing with this for about 7 months now and the situation isn't improving.

This involves software/code I developed over the past 28 months. I do have documentation proving my ownership and timeline.

What are my legal options here? Is it worth pursuing?

Illustrative response

Copyright registration isn't required but it helps a lot with damages.

Illustrative response

A cease and desist letter is usually the first step. Many situations resolve at that stage.