In Photoshop, when the document, tool, filter, task is not responding as you expect it should here is a list of common problems that might be causing you to pull your hair out.
If you’re not seeing of effect of your work –
• You are on the wrong layer. Check which layer you are working on by identifying which one is highlighted, and to see which layer you need by turning layers on and off.
• You have your layer mode in the layers palette set to something other than normal.
• You have your tool mode set to something other than normal.
• You have the tool opacity set to less than 100%
• You have the layer opacity set to less than 100%
• You have an active selection you can’t see – Ctrl D to deselect
• You are working on a separate layer and don’t have the tool set to sample all layers
If Photoshop isn’t behaving as it should-
• Your brush suddenly becomes a crosshair – turn off all caps
• Your options are greyed out and unavailable – decrease the image bits in Image Mode
• Check to make sure you aren’t in Quick Mask
• Cannot save as a jpg – change from 16 bit to 8 bit in Image Mode