If you followed the steps for importing events older than five days but your import isn’t working, here are the most common issues to look for first:
You’re using your project’s API Secret or Token instead of the API Key. To find your API Key, click your name in the upper righthand corner of your Mixpanel project, select Account from the dropdown, and click Projects. This is easily confused with your API Secret or Token, but the distinction is important, as your import will not work if you use the API Secret or Token.
You’re importing events that have not been triggered in the past 30 days. Following import, events will not be displayed in Engagement reports if they have not been triggered for the past 30 days (i.e., they will be automatically hidden from the UI). If you aren't importing any recent events, try firing a "dummy" one with the same name to resurface old events and force the event to appear in the dropdown.
You’re not using valid JSON. You can try using a third-party JSON validator (like this one) to help debug.
If none of these is the problem and you’re still having trouble importing events for your current users, please reach out to email@example.com. Please include a sample HTTP request you are making.