Writing objectives

I would have to assume the finding was that there was no evidence of review of objectives during Management Review, with the criteria being ISO 17025:2017 clause 8.9.2b. My first comment is that your laboratory system should include a procedure and guidelines on how to address such non-conformances.

When doing root cause analysis start by stating what should have been in place (requirement) and what is the real problem (issue) clearly based on the context of having an ISO 17025 management system in place.  Evaluate the impact and why this needs addressing to fix and prevent it or a similar incident from happening again. The depth you go to, in each case, should be decided based on risk.
Using tools like brainstorming and asking questions like why and what will assist you develop your report and get to the root causes. In this case, the requirement is that information regarding the fulfillment of objectives should have been input for an effective management review activity; and the outcome of discussions recorded. Determine, for example, if the requirement is documented in your QMS. Determine whether the objectives were discussed and reviewed but not recorded. It may be caused by a lack of understanding of ISO 17025 requirements, no assigned responsibility, rushed management review, or poorly documented processes. Have a look to see which causes are most likely and then address them through corrective actions.

For more information, have a look at these articles

How to perform management review in ISO 17025 at https://advisera.com/17025academy/blog/2021/05/03/how-to-perform-management-review-in-iso-17025/

Corrective actions principles and root cause analysis in ISO 17025 at https://advisera.com/17025academy/blog/2020/11/04/corrective-actions-principles-and-root-cause-analysis-in-iso-17025/

These ISO 17025 templates could also be of interest:

Complaint, Nonconformity and Corrective Action Procedure at  https://advisera.com/17025academy/documentation/complaint-nonconformity-and-corrective-action-procedure/

Corrective Action Report (CAR) at https://advisera.com/17025academy/documentation/corrective-action-report-car/