B757-200 First Officer reported girt bar failed to retract when ground crew opened door. Escape slide pulled out of disarmed door but did not deploy.

Narrative

I disarmed left and right doors and verified slide lights were out. Opened left door partially. Ground crew opened the remaining way but girt bar had failed to retract. Slide pulled out of door but did not deploy. Cause: Girt bar failed to retract. Suggestions: Once door is cracked check girt bar.