7.8 is pretty old and no longer supported, so the best way would be either deploying a new image and do a fresh install or perform the upgrade in stages (e. g. 7.8 --> 7.10 --> 7.13 --> 8.x). I nothing works, I would reach out to support team and they can help to get in touch with professional services who can help with moving to 8.x.
Please if the below articles are helpful in any way.
https://kb.vmware.com/s/article/89840
https://kb.vmware.com/s/article/85517