Help with Levels

[sallyanne]

Usually when I open the tool for changing levels on a picture nothing happens until I press ok.
Lately as soon as I open the tool the picture turns an ugly blue and will not do anything else.
I did find out that my 'preview' was turned off but I check that it's on everytime now and it has stayed on since I checked it again. What could be wrong with my levels tool?
I normally use it for correcting colours but now it just wants to do it own thing!
I only updated my gimp to 2.10.34 (revision 2) a couple weeks ago, surely its not this. It has worked ok and has just changed in the last couple of days

EDIT: Made a new gimp file by renaming and restarting gimp and it looks ok atm

[rich2005]

Best guess, your image is in indexed mode with limited colours.

example: https://i.imgur.com/g7EcCw5.mp4

edit: reading the post again

Quote:Usually when I open the tool for changing levels on a picture nothing happens until I press ok.
Lately as soon as I open the tool the picture turns an ugly blue and will not do anything else.

or maybe not: Can you share one of the problem images.

[PixLab]

Maybe you did something on another channel and it keeps your last setting
There is 2 ways to reset to default, by channel like (like the 2 arrows going up on the screenshot), and a general reset at the bottom

   

[sallyanne]

Thanks guys. I edited the post. I think I fixed it by making a new profile.

@rich, my first guess was to check the mode of the image, then to make sure it had an alpha channel and I have learnt from experience that some images need flattening before anything else can be done. I have opened a couple images since making the new profile and it seems to be ok now.
@Pix, Maybe I moved something I shouldn't have, Thanks for showing me where the reset is.