This message may appear for one of two reasons. You may have reached your API limits, if this is the case it will replenished in 24 hours. You can check your API limits by following the instructions below. Alternatively you may need to enable API access in Salesforce.
Learn more by reading: How to enable API Access in Salesforce
How to check your API limits in Salesforce
1. Click Setup
2. In Administration Setup, click Company Profile > Company Information.
3. On this page, find a field called API Requests, Last 24 Hours. This will show you your current usage and your maximum limits. If you are over your limit, Ebsta will not be able to 'talk' to Salesforce and you'll get which the Failed Token message rather than search results.