I was experiencing symptoms very similar to Signature verification failed when running zypper refresh, but they did not abate after waiting a couple of days, and none of the other solutions on that page or on other web search hits for the error messages produced were working.
I wanted to post the eventual culprit and solution, in hopes of helping someone else avoid the couple of days of frustration I experienced: Somehow the gpg executable on my laptop had been deleted. I couldn’t reinstall it using zypper, as that relies on gpg, but I was able to download the RPM directly from the OpenSUSE repositories (exact link below). Note that the stack exchange answer opensuse - Where does zypper install the repository or package signing keys? - Unix & Linux Stack Exchange was helpful in diagnosing the problem, because I could manually go through the signature verification steps it lists and find the one that failed.