When building a platform or a market, you need to understand which side is going to pay for your service. They will be probably the hardest to convince and therefore you need to get traction and create a critical mass with the free population.

To get that traction you have to gather info about the potential interest of the non paying side to participate into your platform. Usually people are always ready to subscribe if it is free and if it meets potentially their needs.

How many free subscribers have you managed to get through your landing page ?
If there is still lack of subscribers, try to analyse what are the most wanted lessons by your user so you can start, so you can show lessons providers there is a public for them.

Another way of getting traction is to start with a result based pricing so lessons provider will have to pay for your service only if there is a minimum number of participants.