Connectors are too small, or not visible:

Adjust the connector sizes to the model you are preparing. The Blender default cube is 2 m and so by default very big. The connectors default settings are way smaller. Either adapt your model to a reasonable size, fitting to your printing plans, or upscale the settings of ther connectors to fit to your model. If you f.e. want to cut and connect s.th. in the size of the default cube, use f.e. Pin Diameter (mm): 500 / Pin Length (mm): 500 in the settings of SnapSplit. -> don't forget to also readjust the snap spheres fto fit to your pin sizes.

Connectors are too big:

Don't use millimeters as yous scene scale. It is important to adjust your presets to use -> Unit / metrics -> Adaptive or meters at the moment, to not get wrong connector sizes.