Inbox disappeared.

we were installing the program for the first time and everything looked good. after working with it for awhile the inbox totally disappeared and never came back. read all the other questions but no success. from what I can read the “Application” page or tab is not present as we see none of the normal mail selections. Help… we were setting up two accounts with one being a gmail and the other a local gci account and we could see both accounts fine but now nothing.