Consider using the On-Demand TechSupport feature as the preferred method for collecting tech-support files, with local collection as an alternative when cluster health is degraded.
Use the "On-Demand TechSupport" feature as the preferred method for collecting tech-support files. Try using this method first, as documented in the following guide: Collecting ACI show tech from APIC UI
If the APIC upgrade has failed and the overall health of the cluster is degraded (cluster status in "Data Layer Partially Diverged / Data Layer Partially Degraded Leadership" state), collect local tech-support files on each APIC node individually. This method is documented in the following guide: Collecting Local show tech from CLI of individual ACI nodes