I had the same problem. And indeed it was caused by my self by turning on the option in
Miscellaneous Policies.
Because it reads “On, disable comments and only let administrators log in” and that is what we wanted.
Not expecting that a very alarming message would appear in the top of the dashboard.
” WARNING: The site is in maintenance mode. DO NOT TOUCH ANYTHING! Your changes may get overwritten!”
Since two people work on this site it would be not very practical not to be able to save our work.