External interrupt does not work on Proteus (PIC16F883)
On power up RB0 is set to analog mode, and all digital input on the pin is disabled. To enable digital I/O on RB0-5 you have to clear the appropriate bits in ANSELH. 

ANSELH = 0; will make PORTB inputs digital. 

Since you are using RA0-6 as digital inputs you should also clear ANSEL.