Problem selecting layers

[Doc_Pit]

I've been working on a file.  I have suddenly lost the ability to select individual layers in that file; i.e., selecting a layer does not highlight the layer.  I can toggle the visibility of the layer; however,  alt+click will not hide all other layers.  I can not activate a mask on a layer.  Strangely, I can click on a layer, then shift+click on some other layer in the stack to select (and highlight) a group of layers.  If I duplicate that group into a new document, all operations are normal (highlight a single layer, move from image to mask, alt+click, etc.).  So, it's something to do with that particular file. No layers are locked.  No auto select.

I can easily work around by just duplicating all layers into a new document.  Then, everything is back to normal.  But I would like to know what might be causing the problem just to further my understanding.  Any insight would be greatly appreciated.

[c.pfaffenbichler]

Could you please post a screenshot taken at View > 100% and with the pertinent Panels (Layers, Channels, Options Bar, …) visible?

[Doc_Pit]

Thanks for the reply.  The first image is from a 4K screen, the second may be easier to read.

[c.pfaffenbichler · Accepted solution]

You seem to have activated Quick Mask Mode (Q).

[Doc_Pit]

Thanks very much.