If your Organization has recently updated to Summer ‘19 and you received the following error message when trying to update a Template source file:

Error uploading template. Insert failed. First exception on row 0; first error: INSUFFICIENT_ACCESS_ON_CROSS_REFERENCE_ENTITY, You do not have the level of access necessary to perform the operation you requested. Please contact the owner of the record or your administrator if access is necessary.: []. (taskfeed1)

Solution:

A Taskfeed Admin User or a Salesforce Administrator can push a button in the Taskfeed Application Settings page that will quickly fix the issue.

Just follow these steps:

1. From the Taskfeed tab, open the wrench icon located on the lower left-hand corner.

2.  Select Application Settings

3. Go to the Background Processes tab

4. Find the Template File sharing Reconciliation section and click Run Now.