What four rectangles mean in text messaging

[AC Question]

My girlfriend send me a text message and she only put 4 rectangles
what this means?

 

[VW Maverick]

Welcome.
Sounds like one device is not recognizing an Emoji.

Mav.

 

[ManiacJoe]

Sounds like Maverick is pointing you in the right direction.

Some emojis are standardized, some are not. Apple phones tend to get new emoji before everyone else.