Issue
My SFDC production instance is undergoing Instance Refresh Maintenance in SFDC. Will this impact the SFDC and Marketo sync?
Salesforce Article:
Help And Training Community
Solution
Provided the org ID of your SFDC environment stays the same, it will remain connected to your Marketo instance.
As best practice, double check with your SFDC team that all of your SFDC records will retain their unique IDs after the refresh.
After the refresh occurs, double check that the Marketo connection in Marketo (under Admin > Salesforce) is intact.