Looks like you hit your daily API limit. For large data requests such as adding into an SFDC campaign through Marketo, you are going to use a ton of API calls. A workaround for large adds to SFDC campaigns like this is to check a SFDC field with a Marketo smart campaign and query that field in an SFDC report and add those members to an SFDC campaign that way.
The 24 hour window does not mean that in 24 hours your API daily limit is reset, rather it means that when API calls become available over the course of the next 24 hours, you can use them.
You can reach out to your Account Rep and increase your daily API limit if you see you are getting close to your limit on a regular basis.
Also you can build an SFDC report that monitors how many calls you are using per day.