Three easy fixes are: level the bed again (especially check that the nozzle is not too close or too far from the bed surface), make sure that your printing parameters fit with the materials that you are using (such as the ABS with a 110 Celsius heated build plate), and last-but-not-least, clean the bed of before and after printing -A clean cloth/paper towel with a little Acetone works great.
For example, the difference with PLA and ABS can vary, even based upon a different manufacturer's material characteristics; PLA from one source can react differently than that of another's for any or all given prints made with both. The CraftBot line is impressive with it's ability to conquer and sculpt a wide range of different materials, but with some of the more exotic or diverse filaments, especially in correlation with the object being created, an element of trial and error can be part of the process in order to make "the perfect print". Some rules of thumb, especially when dealing with ABS in contrast to PLA, are that ABS melts and prints at a higher temperature and your gcode/print settings need to be in direct correlation with this, especially with the heated bed. If you are not providing enough heat to the bed while using ABS, chances are that you are going to get a high occurrence of prints not sticking -the CraftBot line has a heated bed over 100 degrees Celsius for a reason, it makes ABS happy!
Other reasons behind your problem may result from rushing the speed on the base layers, this is a more complicated process to tweak and may require altering the settings of CraftWare in the "Advanced" user mode.
Two easier "quick fixes" to not having perfect adhesion are to make a "raft", or additional base layer to support your print, by checking the "raft" feature box in the CraftWare "Foundation" settings in the "Slicer" section you can automatically create an easy to remove bottom support for your print. Also, the use of a glue stick on the surface, applying a layer before printing, adds insurance to the already adhesive surface.