Mode change from rgb to grayscale not working

You may want to read through this help article.

https://helpx.adobe.com/photoshop/using/converting-color-modes.html

@??_?5254 

Perhaps try a thorough reset of Photoshop preferences?

(read this entire text before acting please)

Unexpected behaviour of Photoshop may indicate damaged preferences, which are saved when Photoshop closes.. Restoring preferences to their default settings is a good idea when trying to troubleshoot unexpected behaviours in Photoshop.

When preferences become corrupt, then various issues can occur.

Here’s some info from Adobe about preferences:

Learn how to access and modify Photoshop preferences and customise according to your frequent workflows

https://helpx.adobe.com/photoshop/using/preferences.html#reset_preferences

According to Adobe, manually removing preferences files is the most complete method for restoring Photoshop to its default state. This method ensures that all preferences and any user presets which may be causing a problem are not loaded. More here: https://helpx.adobe.com/photoshop/using/preferences.html#Manually

The process:

1. Quit Photoshop.
2. Navigate to Photoshop's Preferences folder.
   macOS: Users/[user name]/Library/Preferences/Adobe Photoshop [version] Settings
   Windows: Users/[user name]/AppData/Roaming/Adobe/Adobe Photoshop [version]/Adobe Photoshop [version] Settings
    
   Note: The user Library folder is hidden by default on macOS. To access files in the hidden user Library folder, see How to access hidden user library files.
3. Drag the entire Adobe Photoshop [Version] Settings folder to the desktop or somewhere safe for a backup of your settings
4. Open Photoshop.
    New preferences files will be created in the original location.

You may want to back up your settings and custom presets, brushes & actions before restoring Photoshop's preferences.

Here is general info about that:  https://helpx.adobe.com/photoshop/using/preferences.html#BackupPhotoshoppreferences

And here’s an Adobe Quick Tips link as an aid to overall understanding

https://community.adobe.com/t5/photoshop-ecosystem-discussions/quick-tips-how-to-reset-photoshop-preferences/td-p/12502668

Thanks to Digitaldog for this quick and simple method:

Press and hold Alt+Control+Shift (Windows) or Option+Command+Shift (macOS) immediately after launching Photoshop. You will be prompted to delete the current settings.

You can also reset preferences on quit, if Photoshop is running, by going into General Preferences>General>Reset on Quit.

This action only affects the items found in the preferences dialog box. Numerous program settings are stored in the Adobe Photoshop Preferences file, including general display options, file-saving options, performance options, cursor options, transparency options, type options, and options for plug‑ins and scratch disks. Brushes (and lots of other settings) are not affected by the above instructions for deleting preferences.

You may wish to make a screen capture of the settings in the Preferences dialog to reset them prior to deleting this file. 

Before you reset your preferences, in case of future issues, I suggest you make a backup copy as Adobe may need one to check problematic preferences. 

Quit Photoshop.
Go to Photoshop's Preferences folder

Preferences file locations: https://helpx.adobe.com/photoshop/kb/preference-file-names-locations-photoshop.html\

  [on MacOS see: Users/[user name]/Library/Preferences/Adobe Photoshop [version] Settings

  Note for those on macOS: - Be aware that the user Library folder is hidden by default on macOS. More on that here:

  https://helpx.adobe.com/x-productkb/global/access-hidden-user-library-files.html

  In the Finder, open the “Go” menu whilst holding down the Option (Alt) key.

  "Library" will now appear in the list - below the current user's “home” directory. ]

Now you can drag the entire Adobe Photoshop [Version] Settings folder to the desktop or somewhere safe as a backup of your settings.

Note for macOS:

Preference preservation is affected by macOS permissions,

You’ll need to allow Photoshop ‘Full Disk Access’ in your Mac OS Preferences/Security and Privacy

If resetting preferences doesn't fix your issue:

Go to Preferences > Performance... and uncheck Multithreaded Compositing - and restart Photoshop.

Is Photoshop still hanging? 

Go to Preferences > Performance... click Advanced Settings... and uncheck "GPU Compositing" - then restart Photoshop. 

It may even be time to reinstall Photoshop.

It’s recommended that you use the Adobe CC cleaner tool to remove all traces first.

(See above about preserving preferences first, though! It’s worth preserving them unless they are corrupted.)

How and when to use the Creative Cloud Cleaner tool | Advanced steps

https://helpx.adobe.com/creative-cloud/kb/cc-cleaner-tool-installation-problems.html

Uninstall Photoshop BUT make sure to choose the option “Yes, remove app preference”.

Once that process finishes, start the installation process and look into the “Advanced Options”. Uncheck “Import previous settings and preferences” and choose to “Remove old versions”.

neil barstow - adobe forum volunteer,

colourmanagement consultant & co-author of 'getting colour right'

See my free articles on colour management

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@??_?5254 

If the image is currently RGB8 then it should convert to grayscale, so have you tried resetting your preferences after backing up custom actions, brushes etc? Reinstalling doesn't clear user preferences, which could be corrupted.

Are you using Convert to Profile or Image > Mode?

You could try deleting the R and B channels so that the G channel data is used when remapping multichannel mode to grayscale.

Could you please post screenshots of the Grayscale image with the pertinent Panels (Toolbar, Layers, Options Bar, …) and the Image > Mode-menu visible? 

Hi. If you convert it to grayscale, then all options will be active. I am using Photoshop 2025 version. Regards