ssh and potentially other services are failing with the following seen in syslog:
sshd: pam_access(sshd:account): access denied for user
The pam_access module is using the following file and the file is configured to only allow access for certain users.
To test this is the issue you are running into you can comment out the following lines in the associated pam configuration files and test:
#account required pam_access.so
You can also comment out the configured lines in: /etc/security/access.conf and test.
If the access.conf file is no longer required then leaving either the pam configs or the access.conf file commented out is a valid resolution.