Auch, I got the same error as ma.ttias.be pretty much two years ago. I have no idea why it failed, however the solution seemed to work similar to what he suggested.
[Mon Dec 03 15:07:55.871866 2018] [auth_digest:notice] [pid 3352] AH01757: generating secret for digest authentication ... [Mon Dec 03 15:07:55.871892 2018] [auth_digest:error] [pid 3352] (2)No such file or directory: AH01762: Failed to create shared memory segment on file /run/httpd/authdigest_shm.3352 [Mon Dec 03 15:07:55.871897 2018] [auth_digest:error] [pid 3352] (2)No such file or directory: AH01760: failed to initialize shm - all nonce-count checking, one-time nonces, and MD5-sess algorithm disabled [Mon Dec 03 15:07:55.871901 2018] [:emerg] [pid 3352] AH00020: Configuration Failed, exiting
The directory /run/httpd is gone. So recreate it and give correct permissions; This in my case (on Centos 7X was apache instead of httpd)
mkdir /run/httpd chown root.apache /run/httpd chmod 0710 /run/httpd
Another solution, sadly the mystery is not solved.