Hi Frank, thanks for your help and fast response! I'm sorry but I continue experimenting same problem with 1.8.3,
-If I change 'Backend role' from Admin to Editor for example, and save the changes, it's all ok.
-If I change 'Frontend role' from Admin to Editor for example, and save the changes, if I come back to the plugin settings see that it continues in Admin, so the change haven't been saved.
In admin login screen and in maintenance mode screen, if I have wp-debug activated in wp-config, I can see these notices:
Notice: Undefined index: role_frontend in /var/www/vhosts/dam-vr.es/httpdocs/wp-content/plugins/wp-maintenance-mode/wp-maintenance-mode.php on line 435
Notice: Undefined index: role_frontend in /var/www/vhosts/dam-vr.es/httpdocs/wp-content/plugins/wp-maintenance-mode/wp-maintenance-mode.php on line 463
Hope it helps!
Thanks again!