Error to find the informations in the excel file

I am making an experiment where i have to display stimulus on the screen, randomly and for a certain amount of time. I have an excel file with 16x2 columns with the stimulus and the time. Each stimulus is associated with a different time. I need for each task to use only two columns in excel (that are well defined). The stimulus are images, and there is no problem for Psychopy to find the images, and all the names is my excel file are corrects. The issue here is that psychopy doesn’t find the informations, even though when i put the two wanted columns in an other file where all the others columns are absent, it works. It will be way too long to do each task with a separate excel file, so i want to know what to do.
The two columns are named : Fichier_1 and duree_1, and in the stimulus properties i have wrote : $‘stimuli/’ + Fichier_1 (it worked before), and $duree_1 for stop duration. Obviously the right excel file is on the loop. When i try to run the experiment this is the error : TypeError: can only concatenate str (not “NoneType”) to str

Do you have any ideas or need some further informations ?
Thanks

It sounds like you have a blank cell/row in your spreadsheet.

Thanks for you answer. I try checking for blank spaces but there are none. Is it possible for psychopy to not read my excel file if there are too much colomns ?

Does it break on the first trial?

Try using print('Fichier_1', Fichier_1) in Begin Routine to see what is happening to the variable.