Error 515: not connected to a bluetooth device

hi all,i'm newbie in app iventor.
i need your hand.
i would like to command three light bulb by using arduino , 3 channels of a relay and bluetooth HC-05. i've created my own application with mit app inventor.
after the connection there's always a error message like "error 515 not connected to a bluetooth device"
but what make me to wonder why is, the light of the bluetooth hc-05 is already changed after i click to the list picker and selected the bluetooth device. but the error is still appered

Too few information to help you.
Post your .aia and your .ino files and possibly a schematic drawing of your connections.
Another hint is to use a free app like Serial Bluetooth Terminal (on playstore) to verify if your Arduino+HC05 is sending correctly to the app or, on the opposite, if the characters sent by the Terminal app are received by your Arduino.
Also be sure to cross the wires between the HC05 and the Arduino board (i.e. Arduino Tx to HC05 Rx and Arduino Rx to HC05 Tx pins).
Last but not least, if you use the library SoftwareSerial, please be aware to set the baudrate not higher than 38400 and don't use pins 0,1 'cause they are used for the serial monitor. Use pins 10,11 instead.

Look in the Designer to see if you left any Clock Timers enabled at startup.

Also force your Clock Timers to check if BlueTooth is connected before sending or receiving.