Cause When I installed dlib, a python face recognition library, via brew, all openssl series were upgraded to 1.1.1 series, and when I used require in gem or ruby, I got the following error. Library not loaded: /usr/local/opt/openssl/lib/libssl.1.0.0.dylib I get this error quite a bit, so I’ll leave this as a reminder. Coping As a workaround, I reinstalled it with rbenv and that fixed it. rbenv uninstall 2.6.2 && rbenv install 2.