I was having problem with cPanel roundCube webmailer on one of my shared hosting server. This might save some people troublesome when you tried the following. After you have login in your server using SSH and enter the following.
[root@server~]# /usr/local/cpanel/bin/update-roundcube-sqlite --force
This error occurred when roundcube database not update properly you can use following steps to resolve this issue. If this doesn't work, it might means that the database might not even exist. You will have to create it first by doing this
[root@server~]# /usr/local/cpanel/bin/update-roundcube --force [root@server~]# /usr/local/cpanel/bin/update-roundcube-sqlite --force
It should resolve your issue if its error 500.