The required patch binary was not applied to the vCenter image for VCF Ops to utilize.
Log in to VCF Ops and navigate to Build > <vCenter instance> > Binary Management: PATCH BINARIES.
Check if the desired patch binary (e.g. 9.1.0.0200) is present:
If present with Download Status Pending, select each required component (vCenter, NSX, SDDC Manager, ESX) and click DOWNLOAD.
Log in to vCenter, select the target cluster, and navigate to Updates > Image.
Create or edit the image with desired ESXi version (e.g. 9.1.0.0200) and click SAVE.
In VCF Ops, navigate to Build > Lifecycle, select the vCenter under VCF Instances, and open the Image Management tab.
Click IMPORT IMAGE, select Import from a vCenter, choose the desired image (e.g. 9.1.0.0200), and click IMPORT.
Select the vCenter management domain (mgmtdomain), navigate to the Upgrades tab, and click PLAN COMPONENT UPGRADE.
Select the Software Component (ESX), select the Target Version (e.g. 9.1.0.0200), and save the plan.
Under Upgrade Sequence, click CONFIGURE, go to Assign Image to Clusters, and click ASSIGN IMAGE.
Click Run Prechecks to validate cluster health, then click Upgrade Now to begin the patching process.