Some Mac owners see
untrusted_cert_title as an error when attempting to reinstall macOS. This problem arises when the Mac’s system clock is set incorrectly, and you can wind up in a chicken-and-egg problem: without macOS installed, there’s no straightforward way to set the clock, which would let you install macOS.
To create a secure connection, many encryption algorithms require an up-to-date clock. The encryption system wants to check whether a digital certificate that validates the integrity of a piece of software hasn’t yet expired. If the date embedded in the certificate is before the issuance date or after the expiration date, the software rightly balks—and macOS unfortunately spits out an error, as this eventuality wasn’t considered as far back as Mojave. (The problem may have been fixed since.)