yes ,but still the user cannot open
See AlsoFix the Annoying Issue - File Name Too Long on Windows 10 - MiniTool Partition WizardHow to solve the prompt that the file name is too long when opening excel in nas? - Microsoft Q&A[Detail Guide] How to Delete Long File Names in Windows 10Outlook Attachment Size Limits Explained and Managed
Can't open what? We can't see your screen.
Please share details what you are you are doing because while Windows might support long file names, the application that you are running might not.
See Also
How to shorten long file namesOpen a Powershell prompt. Copy and paste in these commands.
$LongFolderPath = "$env:TEMP\" + ("A" * 200) + "\" + ("B" * 200) + "\" + ("C" * 200) $LongFolderPath.LengthNew-Item $LongFolderPath -ItemType Directory Remove-Item $LongFolderPathIf that works, then Windows supports long file names. It should look like this. 
If it fails, then run this command.
reg query HKEY_Local_Machine\SYSTEM\CurrentControlSet\Control\FileSystem /v LongPathsEnabledVerify that it is a REG_DWORD and is set to 0x1. 
