Thanks for the prompt help.
The link you provided was helpful. That did resolve the issue.
For future reference, the following steps were taken:
- Log into WHM.
- Search for SSL.
- Click on "Manage Auto SSL."
- If not already selected, select "Let's Encrypt" as the SSL provider.
- Check to agree to the terms.
- Check: Recreate my current registration with “Let’s Encrypt™”.
- Go to the "Manage Users" tab.
- Search for the username you need an SSL for.
- Click the button: Check "username"
- Optional: Go to the "Logs" tab to verify that it ran correctly.