Do you see adobe media encoder come up At all? I sometimes get encodings fail inside AME after it starts up. Exiting and restarting character animator solves this for me.
Can you run adobe menia encoder directly? You can run it from the adobe launcher app directly. If it fails, is there an error message?
Otherwise have you tried reinstalling the software in case something got corrupted?
Otherwise can you share your hardware here? I wonder if you are running out of memory. Eg in Windows you can bring up task manager and check free memory. If this is a problem try closing other programs.
also, please report back the exact version of character animator and adobe media encoder from the about menu.