I have a problem, I can not save for web (GIF) on windwos 10 Photoshop cc 2017 this message shown me:
Could not complete this operation, An unknown error has occured
What have you done for trouble-shooting so far?
Restoring Preferences after making sure all customized presets like Actions, Patterns, Brushes etc. have been saved might be a good starting point:
Is there anything noteworthy about the image/animation, is it »very big«, »very long«, …?