Labels not showing when layers are grouped

[EloyBonillaPerez]

Good afternoon,
I have a problem with the labels. Before posting I have been looking for related problems and I have not found any that dealt with this topic. My apologies if it exists and I haven't been able to find it.
The problem is that when the layers are grouped the labels are not displayed. If I extract the layer from the grouping, the labels are displayed. Any idea where the problem could be?
Thank you very much in advance.

[AdrianWelsh]

Try clicking on the List By Labeling option at the top of the table of contents to make sure all your check boxes are checked on for labeling:

Also, check your zoom ranges (set to <None> if you don't want a zoom range) and check your expressions to make sure they are not limiting you:

[EloyBonillaPerez]

Hi Adrian,

thank you very much for your time. I forgot to add an important piece of information. It happens with map image layers. With feature labeling works fine. Anyway I tried your suggestion and when the map is loaded it shows the labels, but it I try to change it, just with opening the label menu the labels disappear. I do not know if it is a bug or it is supposed to work like that. 

I have been searching the web and have not found anything related. If it was a bug I guess someone probably would have already said something about it.