LCD modules can be finicky at powerup. I have a software delay
execute before I begin writing to the display to let it stabilise.
You can also try the initialisation code for the display which
usually consists of sending bytes in the list,

retlw 30h           ; display initialisation
retlw 30h
retlw 30h
retlw 38h           ; 2 lines, 5X7 chars
retlw b'00001100'   ; display = on, no cursor or blink
retlw 1h            ; clear display
retlw 6h            ; increment display

I put a delay after the '30h' commands as defined in the display
initialise instructions.

Tony


Just when I thought I knew it all,
I learned that I didn't.