What are two common reasons why a new account marker layer would display an error...

A new account marker layer may display anerror for “bad addresses” if the address on the account record is unknown or invalid, or if the base object has not been configured correctly. A bad address means that the record failed to plot on the map, and it can affect the accuracy and completeness ofthe data visualization. To fix this issue, the user can either drop a pin on the map to manually set the location of the record, or clear the coordinates and set the verified location by dragging the marker. The user can also check the base object configuration under Installed Package | Configure | Base Objects and make sure the address fields are mapped correctly. References: How to handle Maps bad addresses, Drop a pin for bad addresses in Maps, Salesforce Maps Base Objects