Just had this error on the Marketo Sales Insight tab in Salesforce and was able to resolve it! 🙂
What you should try is deleting the scheduled Apex job named "Best Bets Unhide". Even though the job may not be actually running, it was scheduled at some time in the past. Salesforce won't try to execute on an Apex job with the same name.
In Salesforce, Go to Setup > Jobs > Scheduled Jobs
Create a new view with Job Name = Best Bets Unhide to easily find the job
Click on Del to Delete the job
Refresh your browser and try clicking on the Marketo tab again!
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