benannte Gesichter gelöscht - wiederfinden

@Kati35 said: Is there another way to run facial recognition over all existing images again?

The answer is yes.  But before we go to that sledgehammer approach, let me ask a few other questions just to confirm your situation.

• What OS and version of Elements are you using?
• Do you have a backup of your catalog that existed before you deleted the Named People stack?  If so, you can restore the catalog and all of your work up to the time of the backup will be available, including any UnNamed People stacks which you can then continue naming.  This may save you some substantial work.  If you have a full backup of the catalog and media, you can restore the media to the original location of the files and there will be no duplicate files created on your hard drive.  If you have Elements 2021, it has an option to save just the catalog without the media.  If you have chosen to use this option, you only need to restore the backup of the catalog.  This would probably be the best option in your situation.
• If you haven't created a backup of the catalog via Elements, do you have a backup of your C drive that you can restore?  Some backup software will allow you to restore just a single folder to replace the existing one.  In your case you could restore the old catalog folder from your OS backup.
• @Kati35 said:  Individual files from the person are displayed, but these are certainly images that I had not yet assigned.  Are you sure that face recognition has been completed for the files that you deleted from the catalog and reimported?  Check each stack to make sure that the files have not been added to another stack, even to a different person's stack.  Since you told Elements that the person you named was "not this person", it is possible that Elements has assigned the face to someone else's stack - perhaps somebody in the same family who looks alike.
• In the Named People stacks, do you have any stacks with a blue triangle icon next to them.  If so, open the stacks and see if the deleted person's face appears in a grid which asks you to confirm whether the face is X?
• @Kati35 said:  The metadata is written to all files. I tried some folders.... delete and re-import. It works, but it's not effective... my catalog contains about 60,000 items and the person is included in almost every folder. In addition, I have to reassign all persons.  Yes, deleting a folder from the catalog and importing it again would require face recognition of all faces of persons in that folder.  You say that all metadata has beens saved to the files.   Did you save the metadata before you deleted the person's People tags?  If you had already saved the metadata to files before following my suggestion, the tag information will still be available in the file's metadata.  I believe a keyword tag will even remain in the metadata for the person who was deleted.  (I'm not sure about that.) 
• Even if you only saved the metadata after I suggested it, the People tags will be saved for all people that you have named.  If you followed my suggestion and imported all keyword tags when you import the folders again, the People tag information will be imported under the Imported Keyword Tags tab and will still be available to you.  In that case, it is easy to select all of the Imported Keyword Tags for a person and tag them with a People tag.  You can then delete the Imported Keyword tag.

In this case, the imported images will be tagged with a People tag, but their face will not appear until you assign a recognized face to a person.  Instead, it will display a generic icon:

So, now, if you really want to start face recognition all over again and lose all of the face recognition that has been applied so far, go to Edit>Preferences>Media Analysis and click the Reset Face Analysis button.  Note the warning!!

I hope the translation of my post allows you to understand what I have tried to explain.  Feel free to ask any further questions if you are unsure about anything. 

I just tried to reproduce what you have done.  I selected a stack in the Named People room, right-clicked on the profile picture and all named tags were removed from that person.  However, the face for the photos was still recognized.  If I open the photo in the media grid (with People Recognition turned on in the View menu) and hover over the person's face, I get the option to Add Name for that photo.

Similarly, if I go back to the UnNamed People room, the face shows up and can be named there.  You say that the photos do not show up in the UnNamed People room.  Do you have the Hide Small Stacks box unchecked?

If you look in the Media  Grid at the photos of this deleted-name person in full image view, does the Add Name box show up at all?

How many total images do you have in your catalog?  And how many named People stacks do you have?  If all of the face recognition information has truly been deleted, I have the following suggestions:

• First, make a copy of the catalog folder for backup and to use for some trials.  You don't need to backup the media for this purpose, but you should always have a backup of your media.  You can find the location of the Catalog folder in the Help>System Info. dialog.
• Open the backup copy of the catalog in the File>Manage Catalogs dialog, and on the backup copy, save all metadata to the files, by selecting all images and pressing Ctrl+W.   Depending on the size of your catalog, this can take a long time and if you have a large catalog it is best to conduct the operation in smaller segments.
• Delete all folders containing the missing person's photos from the catalog.  Use the Folder panel to do this.  Do not delete the folders in Windows File Explorer.  But first, delete just one folder to make sure that what I am suggesting works for you.
• Import the deleted folder(s) again.  The images should go through the face recognition process again and you will find the person, hopefully, in the UnNamed People room.  You will then be able to tag them again. 
• Note that when you import the files, you will be given the option to import any name tags that appear in the metadata of the files.   It is possible that the deleted person's name will appear.  You should therefore accept the option to import the tags.  These People tags will then appear as Imported Keyword tags. If this happens, it is fairly easy to convert the keyword tags to People tags. 

 I shall await a further response from you before giving you any additional suggestions.