Most of my data is geocoding in cartodb except a handful. I've verified the location exists using google maps but it's still not coding it. For example, here's a location it's unable to code:
3641 S TACOMA AVE TULSA, OK 74107 US
I've attempted to code using city & postal code with no success.
I recommend you to add separating commas between Street, City, State, Zipcode and Country. This allows the system to recognize your addresses better.
Check the result: 
PS: Notice that you can add the commas in a programatic way in your whole table by using a query.
In case you have QGIS installed: you can use Google's (outstanding) geocode functionality easily with the MMQGIS-plugin.
MMQGIS --> Geocode --> Geocode CSV
