When attempting a mail merge:
Mail merge template just spins around in circles and does nothing.
Message appears in MS Word Error: 'The last time you opened 'HandiMerge.dotm', it caused a serious error. Do you still want to open it?'
When merging gets Error: 'this method or property is not available because the document is locked for editing'
Ensure the issue is not with that specific merge document itself by testing another merge document or creating a new word merge.
To resolve these issues:
Go to the Programs and Features on your computer.
Open a Run command by pressing the Windows key + R on your keyboard.
Type appwiz.cpl and click OK.
Ensure the 'Installed On' date of your Microsoft Office\Microsoft 365 program is 28/02/2023 or later.
Navigate to the HSoft\Doc folder.
Rename the HandiMerge.dotm file to HandiMerge.dotmOLD.
Download a new HandiMerge.dotm file here and save it to the HSoft\Doc folder.