I wonder if this is a Windows folder permissions issue.  Depending on if you are Standard or Advanced, in the past, the customization per user was saved to a folder (on the server or workstation, per version).  If the user doesn't have permissions to create or edit files on the folder, it may not save them.  

The KB does have an article about it.  If David's suggestion doesn't work, it also recommends this:

If that does not work. Rename the "Sage 100" folder found in "C:\Users\<Windows logon>\Documents" on the workstation.

Note: The "Sage 100" folder also stores the workstation user's Favorites. So renaming the "Sage 100" folder would result in loss of Favorite shortcuts to tasks such as data entry or report printing.

I don't think grid definitions are stored in those .json files under the user's documents\sage 100 folder.  Pretty sure they are still being stored in SY_GridDefinition.

I don't think grid definitions are stored in those .json files under the user's documents\sage 100 folder.  Pretty sure they are still being stored in SY_GridDefinition.

Yes... in SY_GridDefinition, and if the user is in a VDI environment with a constantly changing workstation name, the entries will never be saved between sessions, since WorkstationName is part of the key.

Karen Stehman, now that you are on 2021, if you are in a VDI environment as Kevin mentioned, you could use Custom Office's Customizer to set defaults for the grid that could be applied to everyone.  You can specify column order, width, location (main or additional grid), and visibility.