'No disc' is showing on tv

After mounting disc in dvd, tv shows 'No disc' after sometime, why is this happening?

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0