You can only get the latest version if you are an active Junior Tier (10USD) or higher patron and have spent at least $20 on the patreon before. (You can do this through one month of the Senior Tier or two months of the Junior Tier subscription.
If you have recently become a Senior Patron, you need to disconnect your account by clicking on the user icon in the top right corner of the launcher. Afterwards, just log in again and you should be prompted to download the newest version.
The Patreon API takes a while to update the total spent for your new tier, so you might need to wait for an hour or so and try again later.