Water seeping into a crawl space
Water infiltration can com from surface water or sub-surface water. 

Surface water is easier to detect and fix. If you have added onto the length of the house, perhaps the surface water cannot run around the end anymore. That water could puddle and seep into the ground and then eventually seep into the crawl space. 

Subsurface water is harder to locate and eliminate. If the ground is so saturated that it can’t flow away from the house, it will flow in the direction of least resistance, which could be into the crawl space...especially if the ground has been disturbed for the new addition. (Water will flow through the disturbed soil before it will flow through the older original excavation.) 

The only way to fix subsurface water problems is to install a perforated drainline in drainrock down below your crawl space and extend the drainline to a location where it can discharge or where you can collect it and then pump it out.