Most webinar platforms have a support service. If you are using GoToWebinar, then you can contact them directly and let them know of the technical difficulties you'd experienced.

It's always best to practice prior to the webinar (as suggested by Randy Tucker). This will help you spot any problems ahead of time. You could even record the practice and then use it as an automated webinar (if done well).

Technical issues are inevitable, so don't feel bad about the setback. Just plan well ahead and ensure the tool you are using is working well.

I'm not a technical person, but if you need any help on webinar strategy and marketing, feel free to reach out.

All the best!