Packer v1.7.0 complains about self-signed cert on one build but not another

VMware vCenter 6.7U3 with self-signed certificate
Packer v1.7.0 on OS X Big Sur

This is strange, I am not sure where the problem is exactly. Two different build .jsons, one works and the other fails.

An Ubuntu 18,04-based build works fine with vsphere-miso. A different .json for Ubuntu 20.04 fails immediately (using the same variables as the 18.04) build with the following error:

Output for failed build for Ubuntu 20.04:

2021/03/30 18:15:14 Running builder: vsphere-iso
2021/03/30 18:15:14 [INFO] (telemetry) Starting builder vsphere-iso
**vsphere-iso: output will be in this color.**
2021/03/30 18:15:14 [INFO] (telemetry) ending vsphere-iso
==> Wait completed after 133 milliseconds 422 microseconds
2021/03/30 18:15:14 machine readable: error-count []string{"1"}
==> Some builds didn't complete successfully and had errors:
2021/03/30 18:15:14 machine readable: vsphere-iso,error []string{"Post \"\": x509: cannot validate certificate for because it doesn't contain any IP SANs"}

Output for successful build for Ubuntu 18.04 (both builds use the same vCenter credentials):

021/03/30 18:13:39 Starting build run: vsphere-iso
2021/03/30 18:13:39 Running builder: vsphere-iso
2021/03/30 18:13:39 [INFO] (telemetry) Starting builder vsphere-iso
2021/03/30 18:13:39 packer-builder-vsphere-iso plugin: No CD files specified. CD disk will not be made.
**==> vsphere-iso: File /Users/x/y/z/packer/a/ubuntu1804/packer_cache/a37af95ab12e665ba168128cde2f3662740b21a2.iso already uploaded; continuing**
**==> vsphere-iso: File [datastorexyz] packer_cache//a37af95ab12e665ba168128cde2f3662740b21a2.iso already exists; skipping upload.**
**==> vsphere-iso: Creating VM...**

SOLVED: I had to read up on the allowed configuration options

"insecure_connection": true