One of the user reported that the inbox folder was renamed to archive

There is one possibility of when the user has clicked on archive folder by accidentally by highlighted inbox – clicking on archive and then use create archive folder or choose existing folder.

while troubleshooting found this is a known issue and there is an article released from Microsoft

https://support.microsoft.com/en-us/help/2826855/folder-names-are-incorrect-or-displayed-in-an-incorrect-language-in-ou 

As per Microsoft this  can also occur if   a mobile device with different application like MDM  or a third-party server application synchronizes the Exchange Server mailbox.It could have been caused by a malfunctioning add-in.

If the default Inbox folder is changed unexpectedly to Archive we need to directly skip to step 4 and not look into step 1,2&3.

Use the step4  with MFCMapi tool to fix this problem.

Once the step4 is completed we need to run resetfolder as below

outlook.exe /resetfoldernames

After performing the step 4 we can run the below command and make sure the inbox folder in the root folder path is renamed correctly and not present as archive.

Get-MailboxFolderstatistics mbxname | select name,folderpath,foldersize,itemsinfolder

Thanks & Regards 

Sathish Veerapandian