Some users have reported an issue with the secure checkout button being blocked. Most users have found success by leaving the failing page and then returning to the event dashboard via app.evvnt.com/events. From there, you can find the event you'd like to upgrade and select the green button to "Upgrade to Premium". In most cases, users do not experience the same issue when retrying from app.evvnt.com.
Typically, this issue is related to an issue with the browser being used. Some browsers may have unknown errors that we have not yet identified. We test our systems on Google Chrome and so we recommend using that browser when using our service. Also, avoiding use the refresh or back button in the browser is recommended when you have entered information into any secure fields.
Another possible explanation of this issue can be that the network being used is preventing a secure payment from being made. If this is possible then please try your purchase again on a different network.
If you continue to experience issues you can reach out to firstname.lastname@example.org.