Q: What does a status change from 'Under Review' to 'Reviewers Assigned' mean?

This status change does occur occasionally. This means that one or more initially assigned peer reviewers were unable to review the manuscript for any or all of a variety of reasons: unavailability, identified conflict of interest, and a mismatch with their field. So, the Associate Editor (AE) looked around for one or more peer reviewers, was able to find one/them, and has now assigned new reviewer(s) to your manuscript. So, now, you need to wait for the next update – for the reviews to be completed.

However, if the status again changes to something similar, it means the AE is having some challenge finding reviewers for your manuscript. If so, you may consider checking with them about this, and even referring reviewers, if you know any.

Hope that helps. For more information on the points discussed above, you may find the following resources useful:

• Why does the status change back to "Reviewers assigned" after 3 days of "Under review"?
• A practical handbook of templates for communicating with the journal

All the best for the next stages on your manuscript!