An error has occurred refreshing 'My OnePlaceMail' folders when logging in Outlook 2013.

One of our customers has reported this ongoing error message when their log in their Outlook 2013 client:

"An error has occurred refreshing 'My OnePlaceMail' folders.

Error: Cannot create the folder.

Click on "Show details" and it expands to below:

Application: Microsoft Outlook
Method: Microsoft.Office.Interop.Outlook.MAPIFolder Add(System.String, System.Object)
Stack Trace:    at Microsoft.Office.Interop.Outlook._Folders.Add(String Name, Object Type)
   at FileToWSSOutlookAddIn.ThisAddIn.CreateRootSharepointFolder()
   at FileToWSSOutlookAddIn.ThisAddIn.GetRootSharepointFolder()
   at FileToWSSOutlookAddIn.ThisAddIn.RefreshOutlookFoldersFromConfigFile(String configFilePath, Boolean startUp, Boolean onlyRefreshIfFavoritesModifiedFlagIsSetInConfigXml)"

Our customer reported this back in November 2017, but I cannot tell if this started back in October 2017 and users decided to report this issue later to us.

Tried the following without success:

-user hive registry changes

-searched for recents.xml in user's profile but non exist
-cleared OPM recent locations
-reset user's profile location
-removed/re-added OPM Add-in
-checked windows security update has been installed:

https://www.howto-outlook.com/news/update-2017-10-ol2013.htm

Our customer is using:

Outlook 2013
MS Office 2013
OPM 6.6.1

Any other ideas to try out? Do I have to upgrade to the latest for this to resolve issue?