this happened to me before, too.

This is very likely when you don't have a direct connection to swiss.com (like in many offices, you have a "proxy server" between your PC and the Swiss website which causes time-outs).

In fact you are check in, but could not print your boarding pass.

So you might call them and verify that you REALLY are check-in. At the airport, you need to collect your boarding pass at the dedicated counter.

There is no way to re-do the web-checkin procedure once it failed.