DH5alpha usually appear overnight, even if small (hold them up to the light). Did you possibly run a positive control for your transformation? That is usually a good idea just to make sure the cells are competent. I assume you are selecting on AMP, thus I always run no plasmid, positive plasmid, and the ligation reaction. Cover your bases.

In my experience, whenever I used DH5α, colonies appeared after about 16 hours of incubation at 37 °C. However, I worked with chemically competent cells, not electrocompetent ones. You might want to check whether the electroporator is functioning properly, and verify the voltage settings and the buffer composition. Each of these factors is crucial for a successful transformation.

It’s also possible that the issue lies with the cells themselves. Are your cells truly electrocompetent? Are they fresh? If they have been stored in the freezer for too long, their competency can decrease significantly, which may explain the lack of colonies.

Another point: I always used 100 µg/mL of ampicillin.

Regarding your plasmid: you mentioned that you extracted it and performed a digestion, but none of the bands corresponded to your insert size. Have you confirmed that you actually obtained the plasmid? Did you perform a PCR? Alternatively, you could do a digestion with a single enzyme that cuts only once in the plasmid and run it on a gel to check if the plasmid has the expected size.

As others have mentioned, you should see colonies 16-24 hours after plating, I don't think there will be much difference whether using chemically competent or electrocompetent. It will be slower than a RecA+ strain but not horribly so. Maybe 50% longer and colonies will be smaller.

However development of the blue color can be slower than colony formation and sometimes you need to wait until the colonies are good sized before you can clearly see the blue color. Do a positive control with some undigested plasmid that should be blue to gauge how long it takes and to ensure your x-gal is good.