This can occur if the vApp Template is tagged with a Compute Policy that no longer exists.
To resolve the issue, you will have to change the VM Placement/vGPU Policy and/or the VM Sizing Policy to "None" on the captured vApp Template.
Details are in the Cloud Director documentation, Assign a VM Placement Policy and a VM Sizing Policy to a vApp Template Using Your VMware Cloud Director Tenant Portal.
For example:
Select Content Hub within the Cloud Director Tenant Portal.
Select Content > vApp Templates.
Click the radio button to the left of the desired vApp Template.
Select TAG WITH COMPUTE POLICIES.
Change the VM Placement/vGPU Policy and/or the VM Sizing Policy to "None".