We have no spark after replacing the top gasket?

The first thing I would look for is a main system ground that was left off during the repair job. Next, is to check the fuses, this guide can help:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

If anything is okay check to make sure the crankshaft angle sensor is plugged in. Can I ask when you say top gasket do you mean valve cover or head gasket? Here is the location of the crankshaft sensor so you can check it out. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.