eraser tool

Try to reset the preferences of Photoshop using the steps described here:

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

It's recommended to backup your settings before resetting the preferences.

See here:  https://helpx.adobe.com/photoshop/using/preferences.html#backup-photoshop-preferences

If this doesn't help we need more informations. 

Which tool or function do you try to use for removing?

Is the appropriate layer is active?

Please provide also a copy of your 'System Info'. This can be get from the Photoshop menu item Help > System Info. There's a copy button in the System Info dialog. Press this button and paste the info into your next forum post.