Reposting from Microsoft Answers to get more traffic and hopefully an answer to the problem.
I created a file in Excel (365 v1809) and put it on SharePoint. The team using the file is accessing it through Excel Online.
Users enter data on one tab, and then other tabs hold pivot tables (with shared pivot cache) which create different operational views of the data.
Scenario1: User adds a new row to the data entry table and refreshes the pivot table.
Outcome: Pivot table refreshes with new data.
Scenario2: User modifies data in existing row of the data entry table and refreshes the pivot table.
Outcome: Refresh does not update the data within the pivot table.
Scenario3: Added a new column to the source data table with a formula that performs a lookup to another tab on the same file. The original value when I added the column (no data) is still present in the Pivot Table even if I refresh through Excel Online. The lookup values in the source data is updating, but not the Pivot Table.
Solutions attempted: 1 - Deleted the Pivot Table and rebuilt 2 - Turned off caching of data for the pivot table
3 - Created distinct pivot cache for each table
4 - Copied file to another SharePoint site, then deleted/replaced the file on the original site (no other changes). This temporarily fixed the issue but it has come back again.
When I use the file from my desktop Excel install the tables refresh normally.