I have overcome a similar issue with a client in the past and it could be one of several issues - but without knowing more and based on the information you provided.

1 - Targeting the wrong people for demos. Find the right people with the problem that your tool helps solve is critical. This is the downfall for many businesses as getting this part wrong makes everything afterwards extremely difficult. It no longer enough to be general with who you help - you need to be VERY specific.

2 - Is a good a step by step education on how your clients are going to be better off with your services than without part of the trial experience...?
Consider also that most people who take a trial that arent really the right fit for you want to click a button and have magic happen for them

2a - following up with a good education driven promotion will be beneficial for your prospects to try again when they need what you have. This is preframing the sale

3 - Are you clear on a demo call and that it is available to your prospect..? I might come back to point 1 targeting the right customer... if you are putting what you have in front of the right people at the right time - you will see a lift in your trial to call sign up... educating on the benefits (point 2) will also help with this.

4 - whats your end objective...? no mention of it.. a sale is what I presume... Is this the actual purpose of your 1on1..? Do you have a sales process or a script template for your calls to convert caller to customer...?
This seems to be where you could convert more of the people you are talking to better.

Quality not quantity

1 - target the right people
2 - educate with results driven expectations
3 - talk & convert with a structured sales call.

Feel free to call if you need a more detailed outline of any of the points mentioned