Hey, I'm a bit late to this answer, but if you're still around here are some ideas.

It would be useful to know how you're acquiring sign ups as it could be something to do with your targeting? If you cover a topic that's too broad, particularly digital, there's really nothing that's going to hook people in and commit them to turning up.

With that in mind...

1. Your reminders/drip system sounds fine. Keep them in place.

2. Do you have any kind of testimonials from previous webinar attendees that can offer any kind of encouragement to future webinar attendees about your legitimacy and what they can expect to get out of it?

If so, seek some out. Put these testimonials in your drip campaigns.

3. Survey the people who didn't turn up. This has worked for me in some instances.

Just sent a one-to-one email. "Hey. I missed you today :(. I'd be happy to send you the video if you still want to? You'll still get access to all the bonuses".

4. Make sure there are bonuses at the end of the video. If they make it all the way to the end of the video, they get access to a special promotion, or further lead gen product or exclusive product. Anything.

5. Consider the copywriting for your drip campaign.

If your audience targeting is generating sign ups, perhaps it's not even the webinar topic, but the copywriting for your drip campaign that's turning people off and not keeping them tuned in.

6. With the last point in mind, consider turning the drip campaign into a mini-course.

E.g. over 4 weeks leading up to the webinar, you release short tips each week related to the topic. Then promise to go into even more detail on the webinar at the end of the course where attendees will also have the chance to answer your questions.

7. Give future webinar attendees access to short videos which demonstrate the type of things they are going to learn from your webinar.

8. Run a webinar with two people.

1 person to deliver the webinar and one person on hand to answer all the live questions in chat. Make users aware in advance that they won't have to wait to the end of the webinar to ask specific questions as you'll have live support.

You're probably already aware but the key thing is to make sure the webinar is not too broad. Keep webinars super-specific and identify the people in advance whose very specific problems you can solve. That way you're more likely to get them to tune in and stay engaged.

Good luck!