Power Pivot Refresh Error - Could not find installable ISAM.

[shanemcgillycuddy]

i have created a relatively simple Power Pivot for a monthly Profit & Loss. when i create the connection with the data intially it refreshes and pulls the data in. However anytime i try to refresh the data after that i get an error. When i click on the workbook connection and test that connection i get this: the test connection failed because the provider could not be initialized. If you contact Microsoft Support about this error, provide the following message: Failed to connect to server. Reason: Could not find installable ISAM.
there is a help document from MS but it is regarding Access databases and regarding changing table names. i am only using Excel worksheet data as the source for me Power Pivot. and both files are saved in the same folder. i have tried it on my PC local folder and where it was originally in our company Google drive. also it happens on the next refresh after connecting. no data has changed.

any ideas what i can try?